Fix twig syntax

Author: Arkalo2

forms.rst

@@ -981,15 +981,15 @@ This is a creation user form::
 
 The extra fields can be injected like this:
 
-.. code-block:: twig
+.. code-block:: html+twig
 
     {# templates/user/create.html.twig #}
     {{ form_start(form) }}
         {{ form_row(form.username) }}
         {{ form_row(form.email) }}
 
         {# Hidden field to send additional sponsorship code #}
-        <input type="hidden" name="user_create[referralCode]" value="{{ referralCode }}" />
+        <input type="hidden" name="user_create[referralCode]" value="{{ referralCode }}"/>
 
         <button type="submit">Submit</button>
     {{ form_end(form) }}