Bump django-stubs from 1.11.0 to 1.12.0

Bumps [django-stubs](https://github.com/typeddjango/django-stubs) from 1.11.0 to 1.12.0.
- [Release notes](https://github.com/typeddjango/django-stubs/releases)
- [Commits](https://github.com/typeddjango/django-stubs/compare/[email protected])

---
updated-dependencies:
- dependency-name: django-stubs
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>