Bump markdown from 3.6 to 3.7

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.6 to 3.7.
- [Release notes](https://github.com/Python-Markdown/markdown/releases)
- [Changelog](https://github.com/Python-Markdown/markdown/blob/master/docs/changelog.md)
- [Commits](Python-Markdown/markdown@3.6...3.7)

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

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

requirements/doc-requirements.txt

@@ -21,7 +21,7 @@ jinja2==3.1.4
     #   mkdocs
     #   mkdocs-material
     #   mkdocstrings
-markdown==3.6
+markdown==3.7
     # via
     #   mkdocs
     #   mkdocs-autorefs