Remove keyguard_indication_area_overlay

The overlay was introduced for SysUIGoogle to customize two icons on
docking UI besides charging text, and is no longer needed.

Fixes: 145250100
Test: atest SystemUITests:KeyguardBottomAreaTest
Test: atest SystemUIGoogleTests:DockIndicationControllerTest
Change-Id: If836fe97c3e394cc98f1a05270bd0023e5b57bed
Merged-In: If836fe97c3e394cc98f1a05270bd0023e5b57bed