textproc/py-sphinx-markdown-tables: Fix runtime with py-markdown 3.4+
- Update version requirement of RUN_DEPENDS: Make sure py-markdown 3.4+ is used
- Bump PORTREVISION for package change
Obtained from: https://github.com/ryanfox/sphinx-markdown-tables/commit/7d0bbd2c851efcc9ba25b1a851924333b923c023