Don't use announceForAccessibility in RecentsView

According to accessibility guidelines, we shouldn't be using this API and definitely not for notifying a user a task has closed, so just removing this use case altogether.

Fix: 386001961
Test: Enable Talkback.
  Open some apps.
  Go to Overview and dismiss an app.
  Talkback shouldn't announce "Task closed".
Flag: EXEMPT bugfix

Change-Id: I1a55017cbd4825103b9a8b93532b06276f28aef6