Update prerequisite-system.md

docs/prerequisite-system.md

@@ -72,6 +72,7 @@ If you have a firewall in front of mailcow, please make sure that these ports ar
 | HTTP(S)             | TCP      | 80/443 | nginx-mailcow     | `${HTTP_PORT}` / `${HTTPS_PORT}` |
 | XMPP (c2s)          | TCP      | 5222   | ejabberd-mailcow  | `${XMPP_C2S_PORT}`               |
 | XMPP (s2s)          | TCP      | 5269   | ejabberd-mailcow  | `${XMPP_C2S_PORT}`               |
+| XMPP (upload)       | TCP      | 5443   | ejabberd-mailcow  | `${XMPP_HTTPS_PORT}`             |
 
 To bind a service to an IP address, you can prepend the IP like this: `SMTP_PORT=1.2.3.4:25`