[flexiglass] Set NSSLC#mMaxAlphaForKeyguard to 1 after LS -> Gone

LockscreenToGoneTransitionViewModel#notificationAlpha remained 0f after
the LS - > Gone transition. This was leaving NSSLC#mMaxAlphaForKeyguard
at 0 after the user has unlocked the device, until the shade was opened.

This was hiding HUNs from the GONE scene.

Bug: 378884599
Test: restart sysui, unlock the device, post a HUN, check if it is shown
Flag: com.android.systemui.scene_container
Change-Id: Ib5bc1deaa3764f04105b0efe34d9acae869a57df