Bump django-stubs from 1.7.0 to 1.12.0 (#45)

Bumps [django-stubs](https://github.com/typeddjango/django-stubs) from 1.7.0 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]>

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

surface/requirements_dev.txt

@@ -7,4 +7,4 @@ pylint-django==2.2.0
 
 # for types
 mypy==0.982
-django-stubs==1.7.0
+django-stubs==1.12.0