Dismiss TV PiP notification right after exiting

Previously it was only dismissed during clean up, but it was delayed
when exiting the PiP. Going back to fullscreen was already dismissing it
immediately.

Bug: 362428392
Test: manual - launcherx dashboard and home screen cards are removed
immediately after closing PiP from both PiP menu or dashboard
controls.
Flag: EXEMPT bugfix

Change-Id: Ia7d254796ee9f76c8f574f2d2e18d718f87349c7