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/nginx/dynmaps.conf

@@ -1,6 +1,5 @@
 server {
   listen 8081;
-  listen [::]:8081;
   index index.php index.html;
   server_name _;
   error_log  /var/log/nginx/error.log;

data/conf/nginx/templates/listen_plain.template

@@ -1,2 +1 @@
 listen ${HTTP_PORT};
-listen [::]:${HTTP_PORT};

data/conf/nginx/templates/listen_ssl.template

@@ -1,2 +1 @@
 listen ${HTTPS_PORT} ssl http2;
-listen [::]:${HTTPS_PORT} ssl http2;