Fix a visibility issue in App Handle w/ Immersive.

We check against captionView visibility to update the captionHandle visibility. What ends up happening is after one =Visible.GONE, captionHandle's visibility will never change again, and since we never update captionView's visibility it will now either always exit early (as we try to update to VISIBLE) or re-update to GONE.

Bug: 406081597
Test: Manual - drag up/down while in immersive mode and see app handle shows/hides
Flag: EXEMPT bugfix
Change-Id: Id90cebd9f41888b8e54ee2324a791a4cb5047159