Add support for SQLAlchemy 2.x #39
Description
SQLAlchemy 2.0 breaks the tests, see https://github.com/gocept/risclog.sqlalchemy/actions/runs/4096449437/jobs/7064100934
So #38 restricts this project to SQLAlchemy < 2.
There should be a v2 compatibility mode in v1.4 but we do not seem to have it activated, so the v2 breaking was a bit of a surprise.