Add ContentObserver to RedactNotificationPreferenceController

- Monitor the LOCK_SCREEN_SHOW_NOTIFICATIONS to decide the enabled/disabled status.

Fixes: 134055112
Test: make RunSettingsRoboTests -j ROBOTEST_FILTER=com.android.settings.notification
Change-Id: I7c7edbe13f47638df69f31d15d863c2088a5774f
1 file changed