refactor: 💡 Clean old mirage code (#1373)

Clean from addon old mirage code that it is not used

addons/auth/tests/dummy/mirage/config.js

@@ -1,22 +0,0 @@
-export default function () {
-  // These comments are here to help you get started. Feel free to delete them.
-  /*
-    Config (with defaults).
-
-    Note: these only affect routes defined *after* them!
-  */
-  // this.urlPrefix = '';    // make this `http://localhost:8080`, for example, if your API is on a different server
-  // this.namespace = '';    // make this `/api`, for example, if your API is namespaced
-  // this.timing = 400;      // delay for each request, automatically set to 0 during testing
-  /*
-    Shorthand cheatsheet:
-
-    this.get('/posts');
-    this.post('/posts');
-    this.get('/posts/:id');
-    this.put('/posts/:id'); // or this.patch
-    this.del('/posts/:id');
-
-    https://www.ember-cli-mirage.com/docs/route-handlers/shorthands
-  */
-}

addons/auth/tests/dummy/mirage/scenarios/default.js

@@ -1,7 +0,0 @@
-export default function (/* server */) {
-  /*
-    Seed your development database using your factories.
-    This data will not be loaded in your tests.
-  */
-  // server.createList('post', 10);
-}

addons/auth/tests/dummy/mirage/serializers/application.js

@@ -1,3 +0,0 @@
-import { JSONAPISerializer } from 'ember-cli-mirage';
-
-export default JSONAPISerializer.extend({});