Tweak PromotedNotificationContentExtractor

Autosubmit caught me before I could upload some tweaks to ag/30087268,
so I'm splitting them out here.

Bug: 369151941
Test: atest PromotedNotificationContentExtractorImplTest NotificationContentInflaterTest NotificationRowContentBinderImplTest
Flag: android.app.ui_rich_ongoing
Flag: com.android.systemui.status_bar_notification_chips
Change-Id: Ib4aa9cc443ebfde4266f9de409b3809f4bf9f187