[SB][Call chip] Add distinctUntilChanged to ongoingCallNotif flow.

Bug: 357170372
Flag: com.android.systemui.status_bar_use_repos_for_call_chip
Test: Start ongoing call -> verify chip still shows
Test: atest ActiveNotificationsInteractorTest
OngoingCallControllerViaRepoTest

Change-Id: I51bcf9f44e362ec7ea5045ed7ecd232b13fe609d