[Flag cleanup] fix_drag_pointer_when_ending_drag

This flag is in trunkfood full for few month. We can clean up the flag
usage of this bug fix.

Bug: 300002193
Bug: 316386865
Test: N/A
Flag: N/A
Change-Id: I6c98222623fa0dd15370bba3a5c5365fce3e4e7c