Bump djangorestframework from 3.9.1 to 3.11.2

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.9.1 to 3.11.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.9.1...3.11.2)

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

requirements.txt

@@ -14,7 +14,7 @@ django-filter==2.0.0
 django-heroku==0.3.1
 django-rest-swagger==2.2.0
 django-templated-mail==1.1.1
-djangorestframework==3.9.1
+djangorestframework==3.11.2
 djangorestframework-jwt==1.11.0
 djangorestframework-simplejwt==4.1.0
 djoser==1.1.5