Remove MODE_UNLOCK_FADING since it's no longer needed

Unlock fading was to make face auth feel faster which is no longer
necessary.

Test: manually test (reach from AoD / pulsing notif from AoD)
Test: atest SystemUITests
Bug: 232539318
Fixes: 230411303
Change-Id: I5788c31f9b5216932ad86de5fcde9560cf9c65dd