test(layout): remove unneeded LayoutModule (#18447)

* test(layout): remove unneeded LayoutModule

LayoutModule is an empty `NgModule` remnant from
before treeshakable providers were introduced. It is
no longer needed in this test.

* fixup! test(layout): remove unneeded LayoutModule

src/cdk/layout/media-matcher.spec.ts

@@ -5,20 +5,13 @@
  * Use of this source code is governed by an MIT-style license that can be
  * found in the LICENSE file at https://angular.io/license
  */
-import {LayoutModule} from './index';
 import {MediaMatcher} from './media-matcher';
-import {async, TestBed, inject} from '@angular/core/testing';
+import {inject} from '@angular/core/testing';
 import {Platform} from '@angular/cdk/platform';
 
 describe('MediaMatcher', () => {
   let mediaMatcher: MediaMatcher;
 
-  beforeEach(async(() => {
-    TestBed.configureTestingModule({
-      imports: [LayoutModule]
-    });
-  }));
-
   beforeEach(inject([MediaMatcher], (mm: MediaMatcher) => {
     mediaMatcher = mm;
   }));