py-itsdangerous: updated to 2.2.0

Version 2.2.0
- Drop support for Python 3.7. :pr:`372`
- Use modern packaging metadata with ``pyproject.toml`` instead of ``setup.cfg``.
  :pr:`326`
- Use ``flit_core`` instead of ``setuptools`` as build backend.
- Deprecate the ``__version__`` attribute. Use feature detection, or
  ``importlib.metadata.version("itsdangerous")``, instead. :issue:`371`
- ``Serializer`` and the return type of ``dumps`` is generic for type checking.
  By default it is ``Serializer[str]`` and ``dumps`` returns a ``str``. If a
  different ``serializer`` argument is given, it will try to infer the return
  type of its ``dumps`` method. :issue:`347`
- The default ``hashlib.sha1`` may not be available in FIPS builds. Don't
  access it at import time so the developer has time to change the default.
  :issue:`375`

(adam)