Update webdriver imports. (#45816)

This is to be able to update the webdriver dependency.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

Author: godofredoc

lib/web_ui/dev/webdriver_browser.dart

@@ -8,7 +8,7 @@ import 'dart:io';
 import 'dart:math';
 
 import 'package:image/image.dart';
-import 'package:webdriver/io.dart' show WebDriver, createDriver;
+import 'package:webdriver/async_io.dart' show WebDriver, createDriver;
 
 import 'browser.dart';
 

lib/web_ui/pubspec.yaml

@@ -45,7 +45,7 @@ dev_dependencies:
   uuid: 4.0.0
   watcher: 1.1.0
   web_socket_channel: any
-  webdriver: 3.0.1
+  webdriver: 3.0.2
   webkit_inspection_protocol: any
   yaml: 3.0.0
   web_test_utils: