Bump djangorestframework from 3.11.2 to 3.12.4

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.11.2 to 3.12.4.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](https://github.com/encode/django-rest-framework/commits)

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

requirements.txt

@@ -71,7 +71,7 @@ django-invitations<1.9.4
 django-recaptcha==2.0.6
 
 # REST
-djangorestframework==3.11.2
+djangorestframework==3.12.4
 djangorestframework-gis==0.17
 djangorestframework-guardian==0.3.0
 drf-extensions==0.7.0