fix(@angular/cli): Functions that return promises must be async

Author: timfrijtersppw

packages/schematics/angular/e2e/files/src/app.po.ts.template

@@ -1,11 +1,11 @@
 import { browser, by, element } from 'protractor';
 
 export class AppPage {
-  navigateTo(): Promise<unknown> {
+  async navigateTo(): Promise<unknown> {
     return browser.get(browser.baseUrl) as Promise<unknown>;
   }
 
-  getTitleText(): Promise<string> {
+  async getTitleText(): Promise<string> {
     return element(by.css('<%= rootSelector %> .content span')).getText() as Promise<string>;
   }
 }