REFACTOR: Use Ember modules for @ember/service

app/assets/javascripts/admin/controllers/admin.js.es6

@@ -1,8 +1,9 @@
+import { inject as service } from '@ember/service';
 import Controller from "@ember/controller";
 import computed from "ember-addons/ember-computed-decorators";
 
 export default Controller.extend({
-  router: Ember.inject.service(),
+  router: service(),
 
   @computed("siteSettings.enable_group_directory")
   showGroups(enableGroupDirectory) {