A pointer that previously triggered onTertiaryLongPressDown will not end up causing a long-press.
This triggers once the gesture loses if onTertiaryLongPressDown has previously been triggered.
- kTertiaryButton, the button this callback responds to.
- LongPressGestureRecognizer.onTertiaryLongPressCancel, which exposes this callback at the gesture layer.
final GestureLongPressCancelCallback? onTertiaryLongPressCancel;