DEV: reduces memory footprint of tests - step 1 (#7591)

test/javascripts/components/keyboard-shortcuts-test.js.es6

@@ -64,6 +64,7 @@ QUnit.module("lib:keyboard-shortcuts", {
 
   afterEach() {
     $("#qunit-scratch").html("");
+    testMouseTrap = undefined;
   }
 });
 

test/javascripts/test_helper.js

@@ -65,8 +65,6 @@ d.write(
   "<style>#ember-testing-container { position: absolute; background: white; bottom: 0; right: 0; width: 640px; height: 384px; overflow: auto; z-index: 9999; border: 1px solid #ccc; } #ember-testing { zoom: 50%; }</style>"
 );
 
-Ember.Test.adapter = window.QUnitAdapter.create();
-
 Discourse.rootElement = "#ember-testing";
 Discourse.setupForTesting();
 Discourse.injectTestHelpers();