Don't let non-touchable windows retain a11y focus

Accessibility services can't see non-touchable windows,
so those windows should not be allowed to have
accessibility focus.

Bug: 70986605
Test: Manually went through bug steps, verified that
double-tapping on the screen has no effect.

Change-Id: I7be72331c5704f7aa99714a01bbb2e336eea15e1