RESTRICT AUTOMERGE Clear the BAL allowlist duration

Clearing BAL privileges of a PendingIntent only cleared the tokens,
but kept the duration based entries. `clearAllowBgActivityStarts` is exclusively used by SystemUI (in NotificationManagerService) and fixing this is part of fixing a security vulnerability (therefore and because this is a low risk change it is not flag guarded).

BYPASS_INCLUSIVE_LANGUAGE_REASON=Using an existing API

Bug: 322159724
Flag: EXEMPT bugfix
Test: atest PendingIntentControllerTest
Merged-In: I88e4df8fe4989fbc26aaa0e672626f3a1042678e
Change-Id: I88e4df8fe4989fbc26aaa0e672626f3a1042678e