docs(updater): note file:// URL support requires Nextcloud 34

Signed-off-by: skjnldsv <skjnldsv@protonmail.com>

Author: skjnldsv

admin_manual/maintenance/update.rst

@@ -269,6 +269,8 @@ Point the updater at any HTTP/HTTPS URL:
 
 For a locally staged archive, use a ``file://`` URL:
 
+.. versionadded:: 34
+
 .. code-block:: bash
 
     sudo -E -u www-data php /var/www/nextcloud/updater/updater.phar \