Bump markdown2 from 2.3.5 to 2.4.0

Bumps [markdown2](https://github.com/trentm/python-markdown2) from 2.3.5 to 2.4.0.
- [Release notes](https://github.com/trentm/python-markdown2/releases)
- [Changelog](https://github.com/trentm/python-markdown2/blob/master/CHANGES.md)
- [Commits](trentm/python-markdown2@2.3.5...2.4.0)

---
updated-dependencies:
- dependency-name: markdown2
  dependency-type: direct:production
...

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

requirements.txt

@@ -3,6 +3,6 @@ django-bootstrap-form==3.4
 django-markdown-deux==1.0.5
 django-pagedown==1.0.5
 django-widget-tweaks==1.4.2
-markdown2==2.3.5
+markdown2==2.4.0
 Pillow==8.2.0
 djangorestframework