* Remove unnecessary PG_DATA environement variable from docker-compose.yml
There is no need to set the PostgreSQL data directory to the default location, it just adds an additional unnecessary line to the docker-compose file.
In addition, the PG_DATA isn't even the correct environment variable name (it should be PGDATA, see: https://hub.docker.com/_/postgres/), so this environment variable was never doing anything to begin with.
* Update docker-compose.dev.yml
* Update docker-compose.prod.yml
* Update docker-compose.test.yml
