Update djangorestframework requirement in /requirements

Updates the requirements on [djangorestframework](https://github.com/encode/django-rest-framework) to permit the latest version.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.12.0...3.14.0)

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

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

requirements/base.txt

@@ -18,7 +18,7 @@ whitenoise[brotli]>=5.1,<5.4    # https://github.com/evansd/whitenoise
 
 # Django REST Framework (DRF)
 # --------------------------
-djangorestframework==3.12.*
+djangorestframework==3.14.*
 djangorestframework-filters==1.0.*
 drf-yasg[validation]==1.20.*