Bump djangorestframework from 3.12.2 to 3.12.4

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.12.2 to 3.12.4.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](https://github.com/encode/django-rest-framework/commits)

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

requirements/base.txt

@@ -6,7 +6,7 @@ django-csp==3.7
 django-csp-reports==1.4
 django-crispy-forms==1.11.1
 django-filter==2.4.0
-djangorestframework==3.12.2
+djangorestframework==3.12.4
 django-toolbelt==0.0.1
 gunicorn==20.0.4
 gviz_api==1.9.0