Update alpha animation for All Apps / Divider icon.

This prevents the icons from lingering as the spring settles for the scaling reveal
home animation.

Bug: 298089923
Test: go from app to home, from overview to home, vice versa
Flag: ACONFIG com.android.launcher3.enable_scaling_reveal_home_animation DISABLED
Change-Id: I6bc3f0fcbdc63f0c064d425c8ebaf62a20451ac1