Bump django from 3.1.8 to 3.1.12

Bumps [django](https://github.com/django/django) from 3.1.8 to 3.1.12.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/3.1.8...3.1.12)

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

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