Bug 1715086 - Remove unnecessary generator from devtools/server/tests/browser/storage-unsecured-iframe.html r=jdescottes

There is no async cleanup here - generator not necessary

Differential Revision: https://phabricator.services.mozilla.com/D117048

devtools/server/tests/browser/storage-unsecured-iframe.html

@@ -16,7 +16,7 @@ sessionStorage.setItem("iframe-u-ss1", "foobar1");
 sessionStorage.setItem("iframe-u-ss2", "foobar2");
 console.log("added cookies and stuff from unsecured iframe");
 
-window.clear = function* () {
+window.clear = function () {
   document.cookie = "uc1=; expires=Thu, 01 Jan 1970 00:00:00 GMT";
   localStorage.clear();
   sessionStorage.clear();