Removed deprecated helper function async

src/app/header/header.component.spec.ts

@@ -1,4 +1,4 @@
-import { async, ComponentFixture, TestBed } from '@angular/core/testing';
+import { ComponentFixture, TestBed, waitForAsync } from '@angular/core/testing';
 import { By } from '@angular/platform-browser';
 import { TranslateModule } from '@ngx-translate/core';
 
@@ -17,8 +17,8 @@ let fixture: ComponentFixture<HeaderComponent>;
 describe('HeaderComponent', () => {
   const menuService = new MenuServiceStub();
 
-  // async beforeEach
-  beforeEach(async(() => {
+  // waitForAsync beforeEach
+  beforeEach(waitForAsync(() => {
     TestBed.configureTestingModule({
       imports: [
         TranslateModule.forRoot(),