devel/py-cookiecutter -- update to 1.7.3

Note: we continue to downrate the requirement on py-requests to 2.22.0
compared to upstream's requirement for >=2.23.0. We are still waiting
on PR250941 before we can correct that.

ChangeLog: https://github.com/cookiecutter/cookiecutter/blob/1.7.3/HISTORY.md