Bump markdown from 3.5.2 to 3.8.1

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.5.2 to 3.8.1.
- [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@3.5.2...3.8.1)

---
updated-dependencies:
- dependency-name: markdown
  dependency-version: 3.8.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ commonmark==0.9.1
 docutils==0.20.1
 feedgenerator==2.1.0
 Jinja2==3.1.6
-Markdown==3.5.2
+Markdown==3.8.1
 markdown-full-yaml-metadata @ git+https://github.com/Holzhaus/python-markdown-full-yaml-metadata@9af69835fa1ca154776a788666280a7019c6c636
 Markdown-Video @ git+https://github.com/Holzhaus/Python-Markdown-Video@98725ee09995fdeb05597d82defacaa7ceeca546
 MarkupSafe==2.1.3