Revert "Add an invisible layer to trap focus"

This reverts commit cb98114abd40b645245bbf9d60195b662b6eba37.

Reason for revert: Not needed once ag/13507782 is merged

Bug: 169372603
Change-Id: I52d4344f6f2f3fb973f3f20e7d6f1ec2844d7567
Test: manually enter PiP
1 file changed