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