Bump django from 3.1 to 3.1.13

Bumps [django](https://github.com/django/django) from 3.1 to 3.1.13.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/3.1...3.1.13)

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

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

requirements.txt

@@ -13,7 +13,7 @@ click==7.1.2
 constantly==15.1.0
 cryptography==3.0
 daphne==2.5.0
-Django==3.1
+Django==3.1.13
 gunicorn==20.0.4
 h11==0.9.0
 hiredis==1.1.0