build(deps-dev): bump django-types from 0.19.1 to 0.20.0 in /backend

Bumps [django-types](https://github.com/sbdchd/django-types) from 0.19.1 to 0.20.0.
- [Changelog](https://github.com/sbdchd/django-types/blob/main/CHANGELOG.md)
- [Commits](https://github.com/sbdchd/django-types/commits)

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

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