fix(@schematics/angular): fix missing link attribute for PWA

packages/schematics/angular/application/other-files/app.component.html

@@ -8,13 +8,13 @@ <h1>
 <h2>Here are some links to help you start: </h2>
 <ul>
   <li>
-    <h2><a target="_blank" href="https://angular.io/tutorial">Tour of Heroes</a></h2>
+    <h2><a target="_blank" rel="noopener" href="https://angular.io/tutorial">Tour of Heroes</a></h2>
   </li>
   <li>
-    <h2><a target="_blank" href="https://github.com/angular/angular-cli/wiki">CLI Documentation</a></h2>
+    <h2><a target="_blank" rel="noopener" href="https://github.com/angular/angular-cli/wiki">CLI Documentation</a></h2>
   </li>
   <li>
-    <h2><a target="_blank" href="https://blog.angular.io/">Angular blog</a></h2>
+    <h2><a target="_blank" rel="noopener" href="https://blog.angular.io/">Angular blog</a></h2>
   </li>
 </ul>
 <% if (routing) { %>