[Safety Labels] Decouple safety label changes from permission rationale

Currently the "Safety Label Changes" feature is toggled on only when the
following two feature flags are enabled:

1. safety_label_change_notifications_enabled
2. permission_rationale_enabled

Remove the dependence on "permission_rationale_enabled", so that "Safety
Label Changes" only relies on the
"safety_label_change_notifications_enabled" flag.

Bug: 269330969
Test:  atest PermissionControllerMockingTests:SafetyLabelChangesJobServiceTest; atest CtsPermission3TestCases:SafetyLabelChangesJobServiceTest;atest CtsPermission3TestCases:AppDataSharingUpdatesTest
Change-Id: Ie82bf6a5b6fe1d8cbe6ab58d23085e01c748b5c3