Add .pause(100) after .pointerUp() to avoid intermittent failure on Firefox

We're still not sure the root cause, but the intermittent failure rate is too high.
So, let's add a hack into the test for now.

Differential Revision: https://phabricator.services.mozilla.com/D252441

bugzilla-url: https://bugzilla.mozilla.org/show_bug.cgi?id=1965673
gecko-commit: 89e714f75f36ce2d9063cc11d9737d6d125d6805
gecko-reviewers: hiro

Author: masayuki-nakano

pointerevents/pointerevent_click_during_parent_capture.html

@@ -240,6 +240,7 @@
         .pointerMove(0, 0, { origin: target })
         .pointerDown()
         .pointerUp()
+        .pause(100) // XXX Required for preventing intermittent failure of Firefox
         .send();
 
       test(() => {