AM: clean up screen pinning toasts.

We remove the unnecessary handler thread logic in LockTaskNotify, as all
toasts are already called from the handler thread in LockTaskController.

Bug: 67934620
Test: bit FrameworksServicesTests:com.android.server.am.LockTaskControllerTest
Change-Id: I5019158b649b7b5f2eac4759dab817fa5f443a76
1 file changed