build(deps): update django-guardian requirement from <2.4.1 to <3.2.1

Updates the requirements on [django-guardian](https://github.com/django-guardian/django-guardian) to permit the latest version.
- [Release notes](https://github.com/django-guardian/django-guardian/releases)
- [Commits](django-guardian/django-guardian@0.1.0...3.2.0)

---
updated-dependencies:
- dependency-name: django-guardian
  dependency-version: 3.2.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements.txt

@@ -33,7 +33,7 @@ django-markdownify==0.9.5
 django-mptt==0.16.0
 django-modeltranslation>=0.11,<0.19.0
 django-treebeard==4.7.1
-django-guardian<2.4.1
+django-guardian<3.2.1
 django-downloadview==2.3.0
 django-polymorphic==3.1.0
 django-tastypie<0.15.0