cleanup: Roll out flag copy_events_for_gesture_detection by deleting usage

This flag was incorrectly tagged as non-bugfix, but is guarding a bugfix.
The flag has been in Trunkfood Full for 2 months.

Bug: 377736692
Flag: android.view.accessibility.copy_events_for_gesture_detection
Test: (existing presubmit; change is a no-op)
Change-Id: I9ccb09d0c1f0441cf79c4046802df7e3aac58c73