Remove unused resources of system bar animations

System bars are controlled by the client now. We don't apply the
traditional window animations to system bars. Those unused XMLs are
removed.

Fix: 256973221
Test: Hide and show system bars by using WindowInsetsTests, and see if
      the animations and the ImmersiveModeConfirmation are as expected.
Change-Id: I90dedd027af4ff67a50ad8820e2573b530c11de5