Remove cruft from test

Author: Steven Orvell

test/unit/disable-upgrade.html

@@ -78,14 +78,6 @@ <h2 id="element">[[prop]]</h2>
 import { Class as PolymerClass } from '../../lib/legacy/class.js';
 import { Polymer } from '../../lib/legacy/polymer-fn.js';
 
-// enable disable upgrade!
-const origPolymerClass = PolymerClass;
-
-Polymer.Class = function(info) {
-  const ctor = origPolymerClass(info);
-  return DisableUpgradeMixin(ctor);
-};
-
 Polymer({
   is: 'x-disabled-legacy',
   properties: {