Pin `docker-compose config`'s version to `3.9`
Pin `docker-compose config`'s version to `3.9`

This avoids bugs on using it's output on swarm

Signed-off-by: Ulysses Souza <9b58b28cc7619bff4119b8572e41bbb4dd363aab@gmail.com>

vdemeester/compose,thaJeztah/compose,vdemeester/compose,thaJeztah/compose