Remove unused method in ClipboardOverlayController

The animateOut() method isn't used; it's superceded by the finish()
methods calling view.getExitAnimation directly. It's not used since the
rollout and removal of the shared transitions flag ag/33238405.

Bug: 409606539
Test: manual (unused method)
Flag: EXEMPT trivial cleanup
Change-Id: I9c6999a1c5563e0e745d5f0bc842739f5e351d9c