Bug 1689240 - Fix intermittent timeout in browser_webext_incognito. r=robwu

This test-only change does fix a TV job failure that I did notice in some of my last push to try
(the one that I did notice was happening on the TV job while running in linux x65 opt build).

Depends on D108514

Differential Revision: https://phabricator.services.mozilla.com/D109668

toolkit/mozapps/extensions/test/browser/browser_webext_incognito.js

@@ -67,11 +67,9 @@ async function setPrivateBrowsingValue(value, id) {
   let radio = getHtmlElem(
     `input[type="radio"][name="private-browsing"][value="${value}"]`
   );
-  EventUtils.synthesizeMouseAtCenter(
-    radio,
-    { clickCount: 1 },
-    radio.ownerGlobal
-  );
+  // NOTE: not using EventUtils.synthesizeMouseAtCenter here because it
+  // does make this test to fail intermittently in some jobs (e.g. TV jobs)
+  radio.click();
   // Let's make sure we wait until the change has peristed in the database
   return changePromise;
 }