textproc/py-mkdocstrings: Add support for Jinja2 3.1
- The newer releases of py-mkdocstrings need some additional dependencies, which are not yet available as ports.
Thus backport a patch of the 0.18.0 release to add compatibility for Jinja2 3.1. This fixes the runtime regarding "contextfunction" that was replaced with "pass_context" in Jinja2 3.1 after 23cc43859179.
- Bump PORTREVISION due package change.