message: docs(router): minor typo
  Fix a minor typo in the description of a router spec.
diff: @@ -36,7 +36,7 @@ describe('Router', () => {
  describe('setUpLocationChangeListener', () => {
  beforeEach(() => { TestBed.configureTestingModule({imports: [RouterTestingModule]}); });
  - it('should be indempotent', inject([Router, Location], (r: Router, location: Location) => {
  + it('should be idempotent', inject([Router, Location], (r: Router, location: Location) => {
  r.setUpLocationChangeListener();
  const a = (<any>r).locationSubscription;
  r.setUpLocationChangeListener();
  