
## Description
This PR adds a call to dispose the internal `MaterialStatesController` instantiated by `_SelectableIconButtonState`.
I found this memory leak while working on M2/M3 test update for `about_test.dart`. This memory leak only happens when using M3 because `IconButton` relies on `_SelectableIconButton` only when useMaterial3 is true:
3a1190a5a8/packages/flutter/lib/src/material/icon_button.dart (L671-L721)
## Related Issue
Fixes https://github.com/flutter/flutter/issues/130708
## Tests
Adds 1 test.