Change docker_compose role so it optionally installs the binary but defaults to the plugin

[gregharvey]

Since the 2.x branch docker-compose no longer exists, or rather, it exists but the preferred approach is to install the docker-compose-plugin package so you make it part of Docker, e.g. docker compose. From now on ce-dev assumes this (although you can change the local config to use docker-config if you wish) so for consistency we should default to installing it that way too.