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] <[email protected]>

Author: dependabot[bot]