Typo fixed on change form.

Author: Doug Van Horn

pyas2/templates/admin/pyas2/mdn/change_form.html

@@ -48,10 +48,10 @@ <h1> View MDN Details</h1>
       </div>
       <div class="form-row field-name">
         <div>
-          <label class="required" >Message Headers:</label>
+          <label class="required" >Payload:</label>
           <p>{{ original.payload|readfilefield|linebreaksbr }}
         </div>
       </div>
     </fieldset>
   </div>
-{% endblock content %}
+{% endblock content %}