Fix PageIndicatorDots Outline

Invalidate the outline when a Folder or WidgetPicker's PageIndicatorDots
become visible with 0 scroll. Necessary to avoid stale Outlines which
appear as grey shadows.

Bug: 394355070
Test: Verified manually that this works well, and looks great in LTR mode and RTL mode.
Flag: com.android.launcher3.enable_launcher_visual_refresh
Change-Id: I3e730b1109b9cd05e25454865f7e97df2078725b