mod_mam_archive: remove invalid disco#info feature The feature which was previously added to disco#info was in fact specified to be used for stream features only (see XEP-0136 section 11). Emitting it in disco#info is weird at best and breaks stuff at worst.

<tr>
  <td colspan="2">
    <script src="https://hcaptcha.com/1/api.js" async defer></script>
    <div class="h-captcha" data-sitekey="{captcha_public_key}"></div>
  </td>
</tr>