Update wordpress.md
Update wordpress.md

Update example to match https://github.com/docker/awesome-compose/blob/master/wordpress-mysql/compose.yaml, which works.
docker/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,thaJeztah/docker.github.io,thaJeztah/docker.github.io,docker/docker.github.io,docker/docker.github.io