ui: remove outdated csrfToken field

packages/ui-default/templates/homework_edit.html

@@ -90,7 +90,6 @@
               markdown:true
           }) }}
           <div class="row"><div class="columns">
-            <input type="hidden" name="csrfToken" value="{{ handler.csrfToken }}">
           {% if page_name == 'homework_edit' %}
             <button type="submit" class="rounded primary button">
               {{ _('Update') }}