DEV: Remove unneeded qunit-helper override

This was leaking on every test... and also doesn't seem to be required. The `examineDockHeader` doesn't exist any more in core, so this was a no-op.

app/assets/javascripts/discourse/tests/helpers/qunit-helpers.js

@@ -14,7 +14,6 @@ import { getApplication, getContext, settled } from "@ember/test-helpers";
 import { getOwner, setDefaultOwner } from "discourse-common/lib/get-owner";
 import { later, run } from "@ember/runloop";
 import { moduleFor, setupApplicationTest } from "ember-qunit";
-import HeaderComponent from "discourse/components/site-header";
 import { Promise } from "rsvp";
 import Site from "discourse/models/site";
 import User from "discourse/models/user";
@@ -213,9 +212,6 @@ export function acceptance(name, optionsOrCallback) {
     beforeEach() {
       resetMobile();
 
-      // For now don't do scrolling stuff in Test Mode
-      HeaderComponent.reopen({ examineDockHeader: function () {} });
-
       resetExtraClasses();
       if (mobileView) {
         forceMobile();