Only requiring 2 taps for accessibility on lock screen

On the lock screen we were requiring two double taps
in order to unlock to a notification, which seems excessive
especially since talkback do their own falsing already.

Test: add notification with talkback on, try double tap
Test: add notification without talkback, existing logic still works
Bug: 32945599
Change-Id: I07e0e4299140644f62d311d8db25ec25ff138fde