security/py-pyhanko: Update to 0.23.1
- Add GitHub to MASTER_SITES
Changes: https://github.com/MatthiasValvekens/pyHanko/releases
https://github.com/MatthiasValvekens/pyHanko/blob/master/docs/changelog.rst https://pyhanko.readthedocs.io/en/latest/changelog.html