Bump markdown from 3.5 to 3.5.1 in /requirements

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.5 to 3.5.1.
- [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...3.5.1)

---
updated-dependencies:
- dependency-name: markdown
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements/main.txt

@@ -17,7 +17,7 @@ drf-yasg==1.21.7
 huey==2.5.0
 hypercorn[h3]==0.15.0
 jsonfield==3.1.0
-markdown==3.5
+markdown==3.5.1
 pwned-passwords-django==2.0
 pyarr==3.1.1
 pymysql==1.0.2