Bump djangorestframework from 3.11.2 to 3.15.2 (#222)

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.11.2 to 3.15.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.11.2...3.15.2)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements-frozen.txt

@@ -9,7 +9,7 @@ django-js-asset==1.2.2
 django-mptt==0.11.0
 django-page-cms==2.0.11
 django-taggit==1.2.0
-djangorestframework==3.11.2
+djangorestframework==3.15.2
 idna==2.8
 isort==4.3.21
 lazy-object-proxy==1.4.3