update requirements+config to SQLAlchemy 2.0
    
    A typing hints plugin is no longer needed. It's recommended to use psycopg
    (version 3) instead of psycopg2.
    
    Manual tasks to do:
    * `pip install -r requirements.txt`
    * Change `postgresql+psycopg2://` to `postgresql+psycopg://` in `conf/settings.py`
    * `pip uninstall psycopg2-binary`
    * `pip uninstall sqlalchemy-stubs`
    
    Related: https://pagure.io/fedora-qa/blockerbugs/issue/266