build(deps): bump django-polymorphic from 3.1.0 to 4.4.1

Bumps [django-polymorphic](https://github.com/jazzband/django-polymorphic) from 3.1.0 to 4.4.1.
- [Release notes](https://github.com/jazzband/django-polymorphic/releases)
- [Changelog](https://github.com/jazzband/django-polymorphic/blob/master/docs/changelog.rst)
- [Commits](jazzband/django-polymorphic@v3.1...v4.4.1)

---
updated-dependencies:
- dependency-name: django-polymorphic
  dependency-version: 4.4.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

requirements.txt

@@ -33,7 +33,7 @@ django-mptt==0.16.0
 django-treebeard==4.7.1
 django-guardian<2.4.1
 django-downloadview==2.3.0
-django-polymorphic==3.1.0
+django-polymorphic==4.4.1
 django-tastypie<0.15.0
 django-tinymce==3.7.1
 django-uuid-upload-path==1.0.0