docker-compose: Remove unused version statement

See https://docs.docker.com/compose/compose-file/04-version-and-name/

> The top-level version property is defined by the Compose
> Specification for backward compatibility. It is only
> informative and you'll receive a warning message that it is
> obsolete if used.

Author: ix5

docker-compose.yml

@@ -1,6 +1,3 @@
-# https://docs.docker.com/compose/compose-file/compose-file-v3/
-version: "3.9"
-
 services:
 
   # Isso server should always reflect production image