Fix issue with acmetool

- https://github.com/chatmail/relay/pull/614#discussion_r2279630626

docker/docker-compose-default.yaml

@@ -43,7 +43,6 @@ services:
       ## system
       - /sys/fs/cgroup:/sys/fs/cgroup:rw # required for systemd
       - ./:/opt/chatmail
-      - ./data/acme:/var/lib/acme
       
       ## data
       - ./data/chatmail:/home

docker/files/entrypoint.sh

@@ -1,6 +1,8 @@
 #!/bin/bash
 set -eo pipefail
 
+unlink /etc/nginx/sites-enabled/default
+
 if [ "${USE_FOREIGN_CERT_MANAGER,,}" == "true" ]; then
     if [ ! -f "$PATH_TO_SSL/fullchain" ]; then
         echo "Error: file '$PATH_TO_SSL/fullchain' does not exist. Exiting..." > /dev/stderr