[flexiglass] UX polish for pattern bouncer appear animation.

Feedback from UX was:
1. Remove the diagonal staggering; dotss to fade in and appear row by row
2. Remove the scaling up of the dots.

Bug: 330475579
Test: manually verified that the animation looks right, also showed to a
UX motion designer in person.
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT

Change-Id: I91bc2fb6c1c20901cf0fec7dd0e8700c230013e1