Always invoke show on the dismiss target for pip.

Previously, if the user moved pip, and then started moving it again
before the dismiss target hide animation finished, the dismiss target
would not show up again, since it was still VISIBLE.

Test: manually, open pip and move it around, dismiss target always shows up
Bug: 242616699

Change-Id: Iac288f5855f0d26075113e795dd2b88b6a152275