Bump django from 3.1.9 to 3.1.12

Bumps [django](https://github.com/django/django) from 3.1.9 to 3.1.12.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@3.1.9...3.1.12)

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

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

requirements.txt

@@ -3,7 +3,7 @@ certifi==2018.1.18
 chardet==3.0.4
 codecov==2.1.4
 coverage==5.3
-Django==3.1.9
+Django==3.1.12
 idna==2.6
 isodate==0.6.0
 nose==1.3.7