Update datepicker format for birthday

Author: Bjorn

Resources/views/Tutorial/datePicker.html.twig

@@ -143,7 +143,7 @@
   <div class="row">
     <div class="col-md-9 col-md-offset-3">
         <pre><code>
-  'format' => DateType::DEFAULT_FORMAT,
+  'format' => IntlDateFormatter::LONG,
   'data' => $dateInThePast,
   'widget' => 'choice',
   'required' => false,