Obsoleting doctopt in favor of doctopt-ng

[Avasam]

When installing the requirements on a fresh install of Python I got the following warning:
DEPRECATION: docopt is being installed using the legacy 'setup.py install' method, because it does not have a 'pyproject.toml' and the 'wheel' package is not installed. pip 23.1 will enforce this behaviour change. A possible replacement is to enable the '--use-pep517' option. Discussion can be found at https://github.com/pypa/pip/issues/8559

That led me to docopt/docopt#502 (comment): even docopt organization members are recommending to switch over to docopt-ng due to docopt being unmaintained in the past 6 years (last release 10 years ago)

https://github.com/jazzband/docopt-ng is py.typed as of 0.8.1 (https://pypi.org/project/docopt-ng/0.8.1)

CC @NickCrews as you added the stubs in #5248