Cleanup flag "floating_menu_narrow_target..."

Full flag name:
"floating_menu_narrow_target_content_observer"

This CL is more involved than other flag cleanup CLs, because removing
the flag in MenuInfoRepository.java removed the need for
AccessibilityManager in that constructor. Removing AccessibilityManager
from the constructor had a cascading effect on other related classes
and tests.

Bug: b/331740049
Test: atest DragToInteractAnimationControllerTest MenuInfoRepositoryTest MenuItemAccessibilityDelegateTest MenuListViewTouchHandlerTest MenuViewTest MenuAnimationControllerTest MenuViewLayerTest
Flag: EXEMPT flag cleanup
Change-Id: I94de6e205aef9bc8bd35798052740c6da929c446