mod_muc_webchat_url: Don't save templated value This prevents changing of other settings without touching the webchat URL from saving the template value. Otherwise the URL will still be advertised when configuring members-only or hidden.

<tr>
  <th>What is {x} {op} {y}?</th><td>
    <input name="captcha_challenge" type="hidden" value="{challenge}">
    <input name="captcha_reply" pattern="[0-9]+" required type="number">
  </td></tr>