Remove pgAdmin and any other extraneous stuff from repo

[jrlegrand]

Problem Statement

We no longer need pgAdmin since we will be using BigQuery.

Airflow probably will still use Postgres locally - it automatically spins up a Postgres container or something - we hijacked that container for all of our SageRx database. We can get rid of the docker-compose up airflow-init call because of this.

Criteria for Success

Hopefully we only have /airflow and /dbt directories in the repo. Hopefully we only need to run docker-compose up to start SageRx.

Additional Information