Re-sort notifications when their bundle classification is removed

The channel reassignment for unclassifying notifications needs to happen as part of signal extraction in order to trigger a re-sorting of the notification list. Otherwise, the notification list reordering would only happen after another notification comes in.

Flag: android.app.notification_classification_ui
Bug: 406491771
Test: NotificationManagerServiceTest, NotificationAdjustmentExtractorTest
Change-Id: Id313bdc0109255bbbbfd65217314eb33cac1d4c5