chore(docsApp): open plnkr.co with HTTPS

Plnkr should be opened via HTTPS instead of HTTP to supress warnings about an insecure connection

Closes #14445

Author: jannickfahlbusch

docs/app/src/examples.js

@@ -153,7 +153,7 @@ angular.module('examples', [])
 
             postData.description = ctrl.example.name;
 
-            formPostData('http://plnkr.co/edit/?p=preview', newWindow, postData);
+            formPostData('https://plnkr.co/edit/?p=preview', newWindow, postData);
           });
 
       };