Bump django from 3.0.14 to 3.1.13

Bumps [django](https://github.com/django/django) from 3.0.14 to 3.1.13.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@3.0.14...3.1.13)

---
updated-dependencies:
- dependency-name: django
  dependency-type: direct:production
...

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

requirements.txt

@@ -1,7 +1,7 @@
 asgiref==3.2.10
 certifi==2020.6.20
 chardet==3.0.4
-Django==3.0.14
+Django==3.1.13
 django-cors-headers==3.4.0
 djangorestframework==3.11.2
 djangorestframework-simplejwt==4.4.0