reverted:
--- b/core/tests/Drupal/FunctionalJavascriptTests/js/JSWebAssert.assertWaitOnAjaxRequest.js
+++ /dev/null
@@ -1,12 +0,0 @@
-(function() {
-  function IsNotAjaxing(instance, index, array) {
-    "use strict";
-    return instance ? !instance.ajaxing : true;
-  }
-  return (
-    // Assert no AJAX request is running (via jQuery or Drupal) and no
-    // animation is running.
-    (typeof jQuery === "undefined" || (jQuery.active === 0 && jQuery(':animated').length === 0)) &&
-    (typeof Drupal === 'undefined' || typeof Drupal.ajax === 'undefined' || Drupal.ajax.instances.every(IsNotAjaxing))
-  );
-}());
\ No newline at end of file