Error: The getter 'subtitle1' isn't defined for the class 'TextTheme'

pub.dev/dropdown_button2-1.9.4/lib/dropdown_button2.dart:1667:51: Error: The getter 'subtitle1' isn't defined for the class 'TextTheme'.

This appears to be due to changes in the Flutter SDK where `subtitle1` has been renamed or deprecated.

**To Reproduce**
Steps to reproduce the behavior:
1. Use Flutter version 3.0.0 (or the latest version as of this writing).
2. Add `dropdown_button2: ^1.9.4` to `pubspec.yaml`.
3. Run the project.
4. See the error in the console output.

**Expected Behavior**
The package should use the updated `TextTheme` properties compatible with the latest Flutter SDK. Specifically, the `subtitle1` should be replaced with `titleMedium` or another appropriate property.

**Proposed Solution**
Update the code in `dropdown_button2.dart` as follows:

```dart
// Original code
style: Theme.of(context).textTheme.subtitle1,

// Updated code
style: Theme.of(context).textTheme.titleMedium,

Could you please update the package to be compatible with the latest Flutter SDK? This would greatly help the community and avoid similar issues in the future.