Update markdown requirement from ~=3.4.3 to ~=3.5.1

Updates the requirements on [markdown](https://github.com/Python-Markdown/markdown) to permit the latest version.
- [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@3.4.3...3.5.1)

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

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

requirements.txt

@@ -1,7 +1,7 @@
 Django~=4.2.7
 pillow~=10.0.1
 django-crispy-forms~=1.14.0
-Markdown~=3.4.3
+Markdown~=3.5.1
 Unidecode~=1.3.6
 Pygments~=2.14.0
 django-mdeditor~=0.1.20