Log Message:
py-markups: update to 4.0.0

There isn't much here of relevance to pkgsrc (as presently configured),
but we may as well track the latest version. This drops Python 3.8
support, but as its only dependant is editors/retext, this doesn't seem
concerning.

Version 4.0.0, 2023-01-16
=========================

Incompatible changes:

* Python versions older than 3.9 are no longer supported.
* Python-Markdown versions older than 3.0 are no longer supported.
* Setuptools 61.2 or higher is required to build the project.
* ``setup.py`` has been removed. Use ``pip``, ``build`` or other :PEP:`517`
  compatible tool.

Other changes:

* Added AsciiDocMarkup (contributed by Dave Kuhlman in #17).
* Made the tests pass with Pygments ≥ 2.11.
* Made the tests pass when PyYAML is not installed (#18).
* Reformatted code in accordance with :PEP:`8` standard.
* Fixed mypy errors and added a :PEP:`561` ``py.typed`` file.