[SB][Notifs] Make notification chips icon-only for now.

There's a lot of work still to do on the text shown in the status bar
notification chips. Since we want to start teamfooding with it ASAP,
remove the text for now and just show the icon.

Bug: 364653005
Flag: com.android.systemui.status_bar_notification_chips
Test: Verify notification chips in status bar only ever show icon
Test: atest NotifChipsViewModelTest

Change-Id: I92eb15765977b94a3ed183013a968909d58f03fc