build(deps): 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] <support@github.com>

requirements.txt

@@ -9,7 +9,7 @@ htmlmin2==0.1.13
 idna==3.7
 Jinja2==3.1.4
 jsmin==3.0.1
-Markdown==3.6
+Markdown==3.7
 MarkupSafe==2.1.5
 mergedeep==1.3.4
 mkdocs==1.6.1