docs: remove docker-compose version

It's obsolete and not used anymore.

See https://docs.docker.com/reference/compose-file/version-and-name/#version-top-level-element-obsolete

Author: jmattheis

docs/install.md

@@ -27,7 +27,6 @@ $ docker run --net=host -e SCREEGO_EXTERNAL_IP=EXTERNALIP ghcr.io/screego/server
 
 **docker-compose.yml**
 ```yaml
-version: "3.7"
 services:
   screego:
     image: ghcr.io/screego/server:GITHUB_VERSION