Bump django-filter from 2.0.0 to 2.1.0

Bumps [django-filter](https://github.com/carltongibson/django-filter) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/carltongibson/django-filter/releases)
- [Changelog](https://github.com/carltongibson/django-filter/blob/master/CHANGES.rst)
- [Commits](carltongibson/django-filter@2.0.0...2.1.0)

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

requirements/base.txt

@@ -5,7 +5,7 @@ dj-static==0.0.6
 django-csp==3.5
 django-csp-reports==1.2
 django-crispy-forms==1.7.2
-django-filter==2.0.0
+django-filter==2.1.0
 djangorestframework==3.9.1
 django-secure==1.0.1
 django-toolbelt==0.0.1