Use PEP 585 type hints

[jsangmeister]

Since https://peps.python.org/pep-0585/, type imports from the typing module are deprecated and should be replaced by the builtin classes or import from collections.abc (e.g. List[str]becomeslist[str]`. This simplifies the typing and removes unnecessary imports.

There exists an automatic upgrade tool (https://github.com/asottile/pyupgrade/) as well as a flake8 plugin to enforce this rule (https://pypi.org/project/flake8-pep585/). I would suggest applying the former and adding the latter to our dev setup.