Remove magnification_enlarge_pointer_bugfix flag.

This flag has been enabled for a while. It is safe to be removed now.

Bug: 409610733
Test: FullScreenMagnificationControllerTest
Flag: EXEMPT removing com.android.server.accessibility.magnification_enlarge_pointer_bugfix
Change-Id: I0362fc1f55221f863d3df457dbe1a29b6fffc2fc