Bump djangorestframework from 3.11.1 to 3.11.2 in /requirements

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.11.1 to 3.11.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.11.1...3.11.2)

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

requirements/base.txt

@@ -44,6 +44,6 @@ graphene>=2.0
 graphene-django>=2.0
 django-solo==1.1.3
 django-cors-headers==3.4.0
-djangorestframework==3.11.1
+djangorestframework==3.11.2
 
 wagtail==2.10