Install PostgreSQL 10 package

[sbesson]

The recent scheduled GitHub actions builds have been failing - see https://github.com/ome/devspace/actions/runs/458408568 and https://github.com/ome/devspace/actions/runs/446236754.

Looking at the logs, the issue is related to the PSQL 9.4 client packages installed in the server and slave Dockerfile which are now EOL and have been removed from the PSQL yum repo.

This PR updates the Dockerfile to:

• use the generic RedHat 7 repository RPM - see https://www.postgresql.org/download/linux/redhat/
• install the PSQL 10 client packages - the version was chosen to be inline with the default postgres image using in docker-compose

[joshmoore]

Makes sense & +1 for keeping things in sync. Can certainly see an upcoming round of bumping to 12 if not 13 across the board.

[sbesson]

Thanks. Merging to fix the scheduled CI builds.