Bug 1646862 - disable browser_DOMDocElementInserted.js on mac and linux 64bits r=jmaher

Differential Revision: https://phabricator.services.mozilla.com/D84088

dom/html/test/browser.ini

@@ -20,6 +20,7 @@ support-files =
   file_bug1108547-3.html
 [browser_content_contextmenu_userinput.js]
 [browser_DOMDocElementInserted.js]
+skip-if = bits == 64 && (os == "mac" || os == "linux") #Bug 1646862
 [browser_form_post_from_file_to_http.js]
 [browser_fullscreen-api-keys.js]
 tags = fullscreen