Flutter 3.22 compatibility

[davestimpert]

After upgrading to Flutter 3.22, I get the following error when building:

../../../.pub-cache/hosted/pub.dev/chips_input-0.1.0/lib/chips_input.dart:603:25: Error: The getter 'subtitle1' isn't defined for the class 'TextTheme'.
 - 'TextTheme' is from 'package:flutter/src/material/text_theme.dart' ('../../../development/flutter/packages/flutter/lib/src/material/text_theme.dart').
Try correcting the name to the name of an existing getter, or defining a getter or field named 'subtitle1'.
        theme.textTheme.subtitle1!.copyWith(height: 1.5).merge(widget.style);