[DO NOT MERGE] Fix regression for enter PIP when onUserLeaveHint

This was changed in ag/15886711, but it shouldn't be needed anymore as
for case we need to animate the close transition, isVisible() will stay
true until the app transition is finished. Otherwise we shouldn't need
to keep the surface as visible even if it is in the closing app list.

Without this fix, we may accidentally show the surface that has been
commited to be invisible, such as enter pip onUserLeaveHint.

Fix: 216145863
Test: manually verify with Google Meet.
Test: atest WmTests:ActivityRecordTests
Change-Id: Ib28651f5c4dc728d19f968adc56015836e307ef8
Merged-In: Ib28651f5c4dc728d19f968adc56015836e307ef8