Dart 3 cleanup: Remove work around for ContinueSwitchStatement crash on web

Once https://github.com/dart-lang/sdk/issues/51802 is resolved, we should remove the work around put in place for it by reverting this commit: https://github.com/flutter/flutter/pull/122546/commits/39d8336fe70c31482f74d1831ce21e95355c5da6