[SliderTheme] Fix markdown links for api doc images (#152748)

Fixes incorrect syntax of image links for the api documentation of the following classes:

- [RectangularSliderTrackShape](https://main-api.flutter.dev/flutter/material/RectangularSliderTrackShape-class.html)
- [RoundedRectSliderTrackShape](https://main-api.flutter.dev/flutter/material/RoundedRectSliderTrackShape-class.html)
- [RectangularRangeSliderTrackShape](https://main-api.flutter.dev/flutter/material/RectangularRangeSliderTrackShape-class.html)
- [RoundedRectRangeSliderTrackShape](https://main-api.flutter.dev/flutter/material/RoundedRectRangeSliderTrackShape-class.html)
- [RoundSliderTickMarkShape](https://main-api.flutter.dev/flutter/material/RoundSliderTickMarkShape-class.html)
- [RoundRangeSliderTickMarkShape](https://main-api.flutter.dev/flutter/material/RoundRangeSliderTickMarkShape-class.html)
- [RoundSliderThumbShape](https://main-api.flutter.dev/flutter/material/RoundSliderThumbShape-class.html)
- [RoundRangeSliderThumbShape](https://main-api.flutter.dev/flutter/material/RoundRangeSliderThumbShape-class.html)
- [RectangularSliderValueIndicatorShape](https://main-api.flutter.dev/flutter/material/RectangularSliderValueIndicatorShape-class.html)
- [RectangularRangeSliderValueIndicatorShape](https://main-api.flutter.dev/flutter/material/RectangularRangeSliderValueIndicatorShape-class.html)
- [PaddleSliderValueIndicatorShape](https://main-api.flutter.dev/flutter/material/PaddleSliderValueIndicatorShape-class.html)
- [PaddleRangeSliderValueIndicatorShape](https://main-api.flutter.dev/flutter/material/PaddleRangeSliderValueIndicatorShape-class.html)

Author: royarg02

packages/flutter/lib/src/material/slider_theme.dart

@@ -1563,8 +1563,7 @@ mixin BaseSliderTrackShape {
 ///
 /// {@macro flutter.material.SliderTrackShape.paint.trackSegment}
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the rectangular slider track shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_slider_track_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the rectangular slider track shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_slider_track_shape.png)
 ///
 /// See also:
 ///
@@ -1665,8 +1664,7 @@ class RectangularSliderTrackShape extends SliderTrackShape with BaseSliderTrackS
 ///
 /// {@macro flutter.material.SliderTrackShape.paint.trackSegment}
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the rounded rect slider track shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rounded_rect_slider_track_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the rounded rect slider track shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rounded_rect_slider_track_shape.png)
 ///
 /// See also:
 ///
@@ -1857,8 +1855,7 @@ mixin BaseRangeSliderTrackShape {
 ///
 /// {@macro flutter.material.RangeSliderTickMarkShape.paint.trackSegment}
 ///
-/// ![A range slider widget, consisting of 5 divisions and showing the rectangular range slider track shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_range_slider_track_shape.png)
+/// ![A range slider widget, consisting of 5 divisions and showing the rectangular range slider track shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_range_slider_track_shape.png)
 ///
 /// See also:
 ///
@@ -1945,8 +1942,7 @@ class RectangularRangeSliderTrackShape extends RangeSliderTrackShape with BaseRa
 ///
 /// {@macro flutter.material.RangeSliderTickMarkShape.paint.trackSegment}
 ///
-/// ![A range slider widget, consisting of 5 divisions and showing the rounded rect range slider track shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rounded_rect_range_slider_track_shape.png)
+/// ![A range slider widget, consisting of 5 divisions and showing the rounded rect range slider track shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rounded_rect_range_slider_track_shape.png)
 ///
 /// See also:
 ///
@@ -2067,8 +2063,7 @@ class RoundedRectRangeSliderTrackShape extends RangeSliderTrackShape with BaseRa
 ///   [SliderThemeData.disabledActiveTrackColor],
 ///   [SliderThemeData.disabledInactiveTrackColor].
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the round slider tick mark shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rounded_slider_tick_mark_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the round slider tick mark shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rounded_slider_tick_mark_shape.png)
 ///
 /// See also:
 ///
@@ -2147,8 +2142,7 @@ class RoundSliderTickMarkShape extends SliderTickMarkShape {
 ///   [SliderThemeData.disabledActiveTrackColor],
 ///   [SliderThemeData.disabledInactiveTrackColor].
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the round range slider tick mark shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/round_range_slider_tick_mark_shape.png )
+/// ![A slider widget, consisting of 5 divisions and showing the round range slider tick mark shape.](https://flutter.github.io/assets-for-api-docs/assets/material/round_range_slider_tick_mark_shape.png)
 ///
 /// See also:
 ///
@@ -2278,8 +2272,7 @@ class _EmptySliderComponentShape extends SliderComponentShape {
 ///
 /// There is a shadow for the resting, pressed, hovered, and focused state.
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the round slider thumb shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/round_slider_thumb_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the round slider thumb shape.](https://flutter.github.io/assets-for-api-docs/assets/material/round_slider_thumb_shape.png)
 ///
 /// See also:
 ///
@@ -2394,8 +2387,7 @@ class RoundSliderThumbShape extends SliderComponentShape {
 ///
 /// There is a shadow for the resting and pressed state.
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the round range slider thumb shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/round_range_slider_thumb_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the round range slider thumb shape.](https://flutter.github.io/assets-for-api-docs/assets/material/round_range_slider_thumb_shape.png)
 ///
 /// See also:
 ///
@@ -2568,8 +2560,7 @@ class RoundSliderOverlayShape extends SliderComponentShape {
 
 /// The default shape of a [Slider]'s value indicator.
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the rectangular slider value indicator shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_slider_value_indicator_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the rectangular slider value indicator shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_slider_value_indicator_shape.png)
 ///
 /// See also:
 ///
@@ -2627,8 +2618,7 @@ class RectangularSliderValueIndicatorShape extends SliderComponentShape {
 
 /// The default shape of a [RangeSlider]'s value indicators.
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the rectangular range slider value indicator shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_range_slider_value_indicator_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the rectangular range slider value indicator shape.](https://flutter.github.io/assets-for-api-docs/assets/material/rectangular_range_slider_value_indicator_shape.png)
 ///
 /// See also:
 ///
@@ -2834,8 +2824,7 @@ class _RectangularSliderValueIndicatorPathPainter {
 /// A variant shape of a [Slider]'s value indicator . The value indicator is in
 /// the shape of an upside-down pear.
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the paddle slider value indicator shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/paddle_slider_value_indicator_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the paddle slider value indicator shape.](https://flutter.github.io/assets-for-api-docs/assets/material/paddle_slider_value_indicator_shape.png)
 ///
 /// See also:
 ///
@@ -2896,8 +2885,7 @@ class PaddleSliderValueIndicatorShape extends SliderComponentShape {
 /// A variant shape of a [RangeSlider]'s value indicators. The value indicator
 /// is in the shape of an upside-down pear.
 ///
-/// ![A slider widget, consisting of 5 divisions and showing the paddle range slider value indicator shape.]
-/// (https://flutter.github.io/assets-for-api-docs/assets/material/paddle_range_slider_value_indicator_shape.png)
+/// ![A slider widget, consisting of 5 divisions and showing the paddle range slider value indicator shape.](https://flutter.github.io/assets-for-api-docs/assets/material/paddle_range_slider_value_indicator_shape.png)
 ///
 /// See also:
 ///