Fix Scrollbar.thickness property is ignored when the Scrollbar is hovered (#144012)
fixes [`Scrollbar.thickness` property is ignored when the `Scrollbar` is hovered](https://github.com/flutter/flutter/issues/143881)
### Code sample
<details>
<summary>expand to view the code sample</summary>
```dart
import 'package:flutter/material.dart';
void main() => runApp(const MyApp());
class MyApp extends StatelessWidget {
const MyApp({super.key});
@override
Widget build(BuildContext context) {
final ScrollController scrollController = ScrollController();
return MaterialApp(
debugShowCheckedModeBanner: false,
home: Material(
child: ScrollConfiguration(
behavior: const NoScrollbarBehavior(),
child: ScrollbarTheme(
data: ScrollbarThemeData(
thickness: MaterialStateProperty.all(25.0),
showTrackOnHover: true,
),
child: Scrollbar(
thickness: 50.0,
thumbVisibility: true,
radius: const Radius.circular(3.0),
controller: scrollController,
child: SingleChildScrollView(
controller: scrollController,
child: const SizedBox(width: 4000.0, height: 4000.0),
),
),
),
),
),
);
}
}
class NoScrollbarBehavior extends ScrollBehavior {
const NoScrollbarBehavior();
@override
Widget buildScrollbar(
BuildContext context, Widget child, ScrollableDetails details) =>
child;
}
```
</details>
### Preview
| Before | After |
| --------------- | --------------- |
| <img src="https://github.com/flutter/flutter/assets/48603081/3537d60d-a5b2-488d-aa99-4c36c3721657" /> | <img src="https://github.com/flutter/flutter/assets/48603081/cfd02095-a327-4b16-8ece-0d1c9e6813ce" /> |
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