mallard-ducktype: autopkg tests fail with setuptools v80:

instead of ignoring the warning, please migrate away from pkg_resources.
It will become RC again.

[...]
184s autopkgtest [19:53:17]: test autodep8-python3:  - - - - - - - - - -
results - - - - - - - - - -
184s autodep8-python3     PASS (superficial)
185s autopkgtest [19:53:18]: @@@@@@@@@@@@@@@@@@@@ summary
185s cli                  PASS
185s library              FAIL stderr:
/usr/lib/python3/dist-packages/mallard/ducktype/extensions/__init__.py:21:
UserWarning: pkg_resources is deprecated as an API. See
https://setuptools.pypa.io/en/latest/pkg_resources.html. The
pkg_resources package is slated for removal as early as 2025-11-30.
Refrain from using this package or pin to Setuptools<81.
185s autodep8-python3     PASS (superficial)