Remove usage of A11y FAB bugfix flags:

- floating_menu_ime_displacement_animation
- floating_menu_overlaps_nav_bars_flag

Both have been in Trunkfood for multiple months.

Bug: 281150010
Bug: 283768342
Flag: ACONFIG com.android.systemui.floating_menu_ime_displacement_animation TRUNKFOOD
Flag: ACONFIG com.android.systemui.floating_menu_overlaps_nav_bars_flag TRUNKFOOD
Test: existing SysUI FAB tests in presubmit
Change-Id: I8ccef66cdc92e92ba9956dff9a051cea3a066342