Bump markdown from 3.7 to 3.8.1

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

@@ -126,7 +126,7 @@ libsass==0.23.0
     # via -r requirements.in
 marisa-trie==1.2.1
     # via language-data
-markdown==3.7
+markdown==3.8.1
     # via -r requirements.in
 markdown2==2.5.3
     # via django-markdown-deux