DisplayContent: Cleanup after tap detector removal

Global tap exclusion regions on a display are no longer used to prevent
focus transfer. Instead, the logic inside onPointerDownOutsideFocus is
used to determine what to do when a non-focused window is touched.

Bug: 311393948
Test: build, presubmit
Change-Id: I32e184ad31eb52119d15d919b4ff283d85e5c7d6