refactor: 💡 remove route-action usage for auth-methods (#2178)

* refactor: 💡 remove route-action usage for auth-methods

✅ Closes: https://hashicorp.atlassian.net/browse/ICU-12603

ui/admin/app/controllers/scopes/scope/auth-methods/new.js

@@ -3,9 +3,11 @@
  * SPDX-License-Identifier: MPL-2.0
  */
 
-import Controller from '@ember/controller';
+import Controller, { inject as controller } from '@ember/controller';
 
 export default class ScopesScopeAuthMethodsNewController extends Controller {
+  @controller('scopes/scope/auth-methods/index') authMethods;
+
   // =services
 
   // =attributes