Don't animate empty shade visibility change when qs expanded

When QS is (close to being fully) expanded, we hide the "No
notifications" text. When we try to animate it out in this scenario,
there's a flicker, so instead let's just update the visibility without
animating since it still looks okay.

We're using the same approach as we do for shouldIncludeFooterView.

Fix: 414321975
Test: manual + NotificationListViewModelTest
Flag: EXEMPT bugfix
Change-Id: I04086f429437242ae1dcd36b91de27d5a1e10836