Remove delayed NSSL visibility

This was only used for devices with side fps, and was used to reduce
the amount of motion when the device was turning on and
unlocking. That unfurling motion has been removed, and hence the need
for the delay. It was also causing notifications to be slightly
visible after unlock.

Fixes: 323240275
Test: manual - look for visible flicker after unlocking side fps
device
Flag: ACONFIG com.android.systemui.keyguard_shade_migration_nssl
DEVELOPMENT

Change-Id: I8c7b17c9950abc64006e3a6255f1e2105350c500