FIX: Desktop Notifications break Qunit tests

We should figure out why they can't run without the conditional in a
browser.

app/assets/javascripts/discourse/initializers/subscribe-user-notifications.js.es6

@@ -56,7 +56,9 @@ export default {
         });
       });
 
-      initDesktopNotifications(bus);
+      if (!Ember.testing) {
+        initDesktopNotifications(bus);
+      }
     }
   }
 };