Fixed the logic when dynamic privacy is enabled

It previously was enabled whenever we were not hiding
lockscreen notifications (most often).
We're now hiding it only when hiding private notification
content, which was always the goal.
This lead to an issue where Clear all was visible.

Fixes: 160709466
Test: atest SystemUITests
Change-Id: Id4f4d598d88c4527abdae9fab025db52c8e8f4c2