chore: remove obsolete docker compose 'version' key

.devcontainer/docker-compose.yml

@@ -1,4 +1,3 @@
-version: '3.8'
 services:
   app:
     image: mcr.microsoft.com/devcontainers/go:1-trixie # https://www.debian.org/releases/trixie/index.en.html