Bump djangorestframework from 3.9.4 to 3.11.2

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.9.4 to 3.11.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.9.4...3.11.2)

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

Author: dependabot[bot]

requirements.txt

@@ -4,7 +4,7 @@ django-easy-pjax==1.2.0
 django-filter==2.2.0
 django-grappelli==2.13.4
 django-material==1.7.1
-djangorestframework==3.10.3
+djangorestframework==3.11.2
 funcparserlib==0.3.6
 funcsigs==0.4
 mock==1.3.0