Bump markdownify from 0.11.6 to 0.13.1

Bumps [markdownify](https://github.com/matthewwithanm/python-markdownify) from 0.11.6 to 0.13.1.
- [Release notes](https://github.com/matthewwithanm/python-markdownify/releases)
- [Commits](matthewwithanm/python-markdownify@0.11.6...0.13.1)

---
updated-dependencies:
- dependency-name: markdownify
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>