Bump django-markdownx from 3.0.1 to 4.0.5

Bumps [django-markdownx](https://github.com/neutronX/django-markdownx) from 3.0.1 to 4.0.5.
- [Release notes](https://github.com/neutronX/django-markdownx/releases)
- [Commits](neutronX/django-markdownx@v3.0.1...v4.0.5)

---
updated-dependencies:
- dependency-name: django-markdownx
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

requirements/base.txt

@@ -11,7 +11,7 @@ django-environ==0.11.2
 django-filter==21.1  # https://github.com/carltongibson/django-filter/
 django-inline-svg==0.1.1
 django-ipware==4.0.2
-django-markdownx==3.0.1  # https://github.com/neutronX/django-markdownx
+django-markdownx==4.0.5  # https://github.com/neutronX/django-markdownx
 django-map-widgets==0.4.2  # https://github.com/erdem/django-map-widgets
 django-model-utils==4.3.1  # https://github.com/jazzband/django-model-utils
 django-modelclone==0.7.1