Fenced frame: attempt to deflake document activeElement test

Like other similar flake fixes, this uses multiClick() to perform
multiple clicks in case one of the clicks doesn't properly register.

Bug: 353256758
Change-Id: Iad904730a8434c52d957353da2a940ad794ac88c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5762702
Commit-Queue: Liam Brady <lbrady@google.com>
Reviewed-by: Andrew Verge <averge@chromium.org>
Commit-Queue: Andrew Verge <averge@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1337300}

fenced-frame/document-activeelement.https.html

@@ -17,10 +17,7 @@
 
   assert_equals(document.activeElement, document.body);
 
-  await actions.pointerMove(0, 0, {origin: fencedframe.element})
-               .pointerDown()
-               .pointerUp()
-               .send();
+  await multiClick(0, 0, fencedframe.element, 5);
 
   assert_equals(document.activeElement, fencedframe.element);
 }, 'document.activeElement should be the fenced frame when it has focus');