Inline notif pipeline flag in NotifEntryManager

This change is a no-op; the flag is now enabled-by-default, so all
removed code paths here are effectively dead.

Bug: 200269355
Test: atest SystemUITests
Change-Id: I6a04d1c238ea938a60cc2bb1f28d780480ad67fd
Merged-In: I6a04d1c238ea938a60cc2bb1f28d780480ad67fd