fix(doc): update CodePen community url

Fixes #6652.

Author: ThomasBurleson

docs/app/partials/getting-started.tmpl.html

@@ -14,7 +14,7 @@
     <p></p>
     <h2>How do I start with Angular Material?</h2>
     <ul style="margin-bottom: 2em;">
-      <li><a href="https://codepen.io/collection/AxKKgY/" target="_blank"
+      <li><a href="http://codepen.io/team/AngularMaterial/" target="_blank"
              title="Link opens in a new window">Visit the Angular Material CodePen Community </a></li>
 
       <li><a href="https://github.com/angular/material-start/tree/es5-tutorial" target="_blank"