Bug 1530282 - Replace promiseWaitForEvent with BrowserTestUtils.waitForEvent r=johannh

Differential Revision: https://phabricator.services.mozilla.com/D37663

--HG--
extra : moz-landing-system : lando

browser/base/content/test/general/browser_visibleFindSelection.js

@@ -14,7 +14,10 @@ add_task(async function() {
 
   let remote = gBrowser.selectedBrowser.isRemoteBrowser;
 
-  let findBarOpenPromise = promiseWaitForEvent(gBrowser, "findbaropen");
+  let findBarOpenPromise = BrowserTestUtils.waitForEvent(
+    gBrowser,
+    "findbaropen"
+  );
   EventUtils.synthesizeKey("f", { accelKey: true });
   await findBarOpenPromise;