Bump markdown from 3.6.0 to 3.7 in /requirements

Bumps [markdown](https://github.com/Python-Markdown/markdown) from 3.6.0 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] <[email protected]>

requirements/main.txt

@@ -17,7 +17,7 @@ drf-yasg==1.21.7
 huey==2.5.1
 hypercorn[h3]==0.17.3
 jsonfield==3.1.0
-markdown==3.6.0
+markdown==3.7
 pwned-passwords-django==2.1
 pyarr==5.2.0
 pymysql==1.1.1