Bump markdown from 3.7 to 3.9

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.7 to 3.9.
- [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@3.7...3.9.0)

---
updated-dependencies:
- dependency-name: markdown
  dependency-version: '3.9'
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -22,7 +22,7 @@ sphinxcontrib.datatemplates==0.11.0
 meetup-api==0.1.1
 urllib3[secure]==2.2.3
 yamale==4.0.4
-markdown==3.7
+markdown==3.9
 ruamel.yaml==0.18.14
 lxml==4.8.0
 # For emoji