Send a gesture tap in touchadjustment/focusout-on-touch.html

Touch adjustment is performed on gestures (not touches), so change
this test to use eventSender.gestureTap() instead of
eventSender.touchStart(). Also unskip this test in TestExpectations.

BUG=261276

Review URL: https://chromiumcodereview.appspot.com/24237006

git-svn-id: svn://svn.chromium.org/blink/trunk@158056 bbb929c8-8fbe-4397-9dbb-9b2b20218538