Update docker compose configuration

- Docker compose file format is now "compose.yml"
- "version" field is deprecated
- mercure docker runs without the command line (it actually was not working anymore)

compose.override.yml

@@ -1,5 +1,3 @@
-version: '3'
-
 services:
 ###> symfony/mercure-bundle ###
   mercure:

compose.yml

@@ -1,5 +1,3 @@
-version: '3'
-
 services:
 ###> symfony/mercure-bundle ###
   mercure:
@@ -12,8 +10,6 @@ services:
       # Set the URL of your Symfony project (without trailing slash!) as value of the cors_origins directive
       MERCURE_EXTRA_DIRECTIVES: |
         cors_origins https://127.0.0.1:9044
-    # Comment the following line to disable the development mode
-    command: /usr/bin/caddy run --config /etc/caddy/Caddyfile.dev
     volumes:
       - mercure_data:/data
       - mercure_config:/config