Bump djangorestframework from 3.9.0 to 3.11.2

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.9.0 to 3.11.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.9.0...3.11.2)

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

requirements.txt

@@ -27,7 +27,7 @@ django-celery-beat==2.0.0
 django-celery-results==1.1.2
 django-db==0.0.7
 django-timezone-field==4.0
-djangorestframework==3.9.0
+djangorestframework==3.11.2
 djangorestframework-jwt==1.11.0
 django-mptt==0.10.0
 et-xmlfile==1.0.1