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.txt

@@ -6,7 +6,7 @@ joblib==1.4.2
 jsmin==3.0.1
 livereload==2.7.0
 lunr==0.7.0.post1
-Markdown==3.6
+Markdown==3.7
 markdown-include==0.8.1
 MarkupSafe==2.1.5
 mkdocs==1.6.1