Bump djangorestframework from 3.4.1 to 3.11.2 in /requirements

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.4.1 to 3.11.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.4.1...3.11.2)

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

Author: dependabot[bot]

requirements/base.txt

@@ -14,7 +14,7 @@ psycopg2-binary==2.7.7
 Pillow==2.8.1
 
 # Rest Framework
-djangorestframework==3.4.1
+djangorestframework==3.11.2
 # rest-pandas==1.1.0
 # patched version to make it python 2 compatible
 -e git+https://github.com/hacklabr/django-rest-pandas#egg=rest-pandas