[flynt] add fix safety section (FLY002) (#17496)

The PR add the fix safety section for rule `FLY002` (#15584 )

The motivation for the content of the fix safety section is given by the
following example

```python
foo = 1
bar = [2, 3]

try:
    result_join = " ".join((foo, bar))
    print(f"Join result: {result_join}")
except TypeError as e:
    print(f"Join error: {e}")
```

which print `Join error: sequence item 0: expected str instance, int
found`

But after the fix is applied, we have

```python
foo = 1
bar = [2, 3]

try:
    result_join = f"{foo} {bar}"
    print(f"Join result: {result_join}")
except TypeError as e:
    print(f"Join error: {e}")
```

which print `Join result: 1 [2, 3]`

---------

Co-authored-by: dylwil3 <dylwil3@gmail.com>

Author: VascoSch92

crates/ruff_linter/src/rules/flynt/rules/static_join_to_fstring.rs

@@ -28,6 +28,14 @@ use crate::rules::flynt::helpers;
 /// f"{foo} {bar}"
 /// ```
 ///
+/// # Fix safety
+/// The fix is always marked unsafe because the evaluation of the f-string
+/// expressions will default to calling the `__format__` method of each
+/// object, whereas `str.join` expects each object to be an instance of
+/// `str` and uses the corresponding string. Therefore it is possible for
+/// the values of the resulting strings to differ, or for one expression
+/// to raise an exception while the other does not.
+///
 /// ## References
 /// - [Python documentation: f-strings](https://docs.python.org/3/reference/lexical_analysis.html#f-strings)
 #[derive(ViolationMetadata)]