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] <[email protected]>

Author: dependabot[bot]

requirements_dev.txt

@@ -7,7 +7,7 @@ falcon==3.0.0; python_version>="3.0"
 flask
 django==1.11.29; python_version<"3.0"
 django==2.2.18; python_version>="3.0"
-djangorestframework==3.9.4
+djangorestframework==3.11.2
 requests==2.22.0
 responses==0.10.12
 webob