[Predictive Back] Fix predictive back swipe on task bar all apps [1/n]

For taskbar all apps, the background scrim is child view of AbstractSlideInView, thus scaling AbstracSlideInView during PB swipe will scale down background scrim. There is no need to re-apply scale effect on background scrim separately.

Bug: 327490078
Flag: aconfig com.android.launcher3.enable_predictive_back_gesture TEAMFOOD
Test: manual
Change-Id: I125670d14bc788664a1371008589e4106496ae2e