fix docker-compose deprecation warning

nm2107 · nm2107 · commit dfcca3c4b780 · 2024-08-22T14:09:20.000+02:00
```
WARN: docker-compose.yml: `version` is obsolete
```

so we're removing the now obsolete `version` attribute.
diff --git a/docker-compose.yml b/docker-compose.yml
@@ -1,6 +1,4 @@
 ---
-version: '3.7'
-
 services:
   app:
     build:
