doc: remove reference to unexisting ESA auth handler

same as in #9275

guides/requests/index.md

@@ -301,7 +301,7 @@ Most applications will desire to have a single `RequestManager` instance, which
 ```ts
 import RequestManager from '@ember-data/request';
 import Fetch from '@ember-data/request/fetch';
-import Auth from 'ember-simple-auth/ember-data-handler';
+import Auth from 'app/services/ember-data-handler';
 
 export default class extends RequestManager {
   constructor(args?: Record<string | symbol, unknown>) {