Update docker-compose.yml examples to use Compose v2

[mdukat]

As of commit https://github.com/CERT-Polska/n6/commit/35117913da19c16d578a3a399ca3d00f95049287, docker-compose.yml contains additional_contexts which requires Compose v2.

This PR changes commented examples with old docker-compose commands, which may let users use unsupported Compose v1, with newer docker compose.