Update markdown requirement from <3.6,>=3.2 to >=3.2,<3.8

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@3.2...3.7)

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

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

Author: dependabot[bot]

requirements/base.txt

@@ -1,6 +1,6 @@
 django>=4.2,<5.2
 djangorestframework>=3.15.2,<3.16
-markdown>=3.2,<3.6
+markdown>=3.2,<3.8
 django-filter>=2.4,<24.4
 django-cors-headers>=4.0,<4.5
 django-userforeignkey>=0.3,<0.6