test(docs-infra): use existing `MockLogger` class in `SwUpdatesService` tests (#39651)

Since we have a `MockLogger` class in `src/testing/`, there is no need
to create a new `MockLogger` class for the `SwUpdatesService` unit
tests.

This commit switches to using the `MockLogger` class from
`src/testing/`.

PR Close #39651

aio/src/app/sw-updates/sw-updates.service.spec.ts

@@ -4,6 +4,7 @@ import { SwUpdate } from '@angular/service-worker';
 import { Subject } from 'rxjs';
 
 import { Logger } from 'app/shared/logger.service';
+import { MockLogger } from 'testing/logger.service';
 import { SwUpdatesService } from './sw-updates.service';
 
 
@@ -204,10 +205,6 @@ class MockApplicationRef {
   isStable = new Subject<boolean>();
 }
 
-class MockLogger {
-  log = jasmine.createSpy('MockLogger.log');
-}
-
 class MockSwUpdate {
   $$availableSubj = new Subject<{available: {hash: string}}>();
   $$activatedSubj = new Subject<{current: {hash: string}}>();