Fallback to clear disable_gesture_pip_animating

From the bug-report, we do see a series of events
- YT enters PiP
- Another app launches, triggers KCA update
    - sendOnPipTransitionStarted is called, sets the flag
- Somehow, wm_task_moved is triggered around the same time
    - which could be due to Activity#moveTaskToBack call originated from
      the app
- pinned task is removed as a result
    - there is no paired sendOnPipTransitionFinished observed

Work around this issue by forcefully clear the
disable_gesture_pip_animating flag when it's not in pip anymore though
we are unable to reproduce the bug.

Flag: EXEMPT bugfix
Bug: 365084002
Test: manually
Change-Id: I4a1d1882a526070c7826d95525599a42c38a52a7