remove setup.sh script

The setup.sh file in backend/database/setup prevents the docker container used during development to start.

• first because, on MacOS at least, a chmod +x is necessary to make the file executable.
• second because, even when executable, the script expects an environment variable, that is useless for development and doesn't exist. Even with the environment variable set, The script does:

rare-basket-postgres | /usr/local/bin/docker-entrypoint.sh: running /docker-entrypoint-initdb.d/setup.sh
rare-basket-postgres | Enter password for new role: 
rare-basket-postgres | Enter it again: 
rare-basket-postgres | SELECT pg_catalog.set_config('search_path', '', false)
rare-basket-postgres | NOTICE:  empty string is not a valid password, clearing password
rare-basket-postgres | CREATE ROLE rarebasket_dev PASSWORD 'md55321bf328c21de137e9e01383241bcf7' NOSUPERUSER NOCREATEDB NOCREATEROLE INHERIT LOGIN;

i.e. the password is autogenerated and thus unusable in the code, since it is unknown before the script runs.

I guess this script is somehow executed manually when deploying the application, but the directory backend/database/setup is not supposed to host deployment-related scripts. It's only purpose is to configure the docker container used during development. So this file should be deleted, or moved elsewhere if it has a purpose.