Paste the following code to the file
/dokuwiki/conf/lang/en/lang.php (create this file if it does not exist):
* Customization of the en language file
* Copy only strings from lang.php which you will modify.
* The remaining strings are read from the original file.
$lang['email_signature_text'] = 'This mail was generated by DokuWiki at https://historial-scouts7montevideo.org/DokuWiki/doku.php?id=wikihistorial7o:inicio';
This overrides the standard message. Your proper link should show up in the emails, now.