ui: remove outdated csrfToken field

packages/ui-default/templates/problem_import.html

@@ -5,7 +5,6 @@
     <div class="section">
       <div class="section__body">
         <form method="post" enctype="multipart/form-data">
-          <input type="hidden" name="csrfToken" value="{{ handler.csrfToken }}">
           <p>{{ _('Upload zipfile') }} {% if type %}({{ _('Type') }}: {{type}}){% endif %}:
             <input type="file" name="file">
             {% if handler.user.hasPriv(PRIV.PRIV_EDIT_SYSTEM) and not type %}<input type="checkbox" name="keepUser">{% endif %}