Make use of docker-compose.override.yml to track changes + completely disable ipv6

https://cloud.gnous.fr/apps/deck/#/board/4/card/25
https://docs.mailcow.email/post_installation/firststeps-disable_ipv6/

data/conf/dovecot/dovecot.conf

@@ -159,7 +159,7 @@ service lmtp {
   }
   user = vmail
 }
-listen = *,[::]
+listen = *
 ssl_cert = </etc/ssl/mail/cert.pem
 ssl_key = </etc/ssl/mail/key.pem
 userdb {