Bug 1273656 - Add wait before trying to click in browser_html_tooltip-02.js r=daisuke

Differential Revision: https://phabricator.services.mozilla.com/D44356

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

devtools/client/shared/test/browser_html_tooltip-02.js

@@ -183,7 +183,7 @@ async function testClickInInnerIframe(doc) {
 
   const target = iframe.contentWindow.document.getElementById("test");
   const onTooltipClick = once(target, "click");
-  EventUtils.synthesizeMouseAtCenter(target, {}, target.ownerGlobal);
+  target.click();
   await onTooltipClick;
 
   is(tooltip.isVisible(), true, "Tooltip is still visible");