build(deps): bump django from 4.0.4 to 4.0.6 in /backend

Bumps [django](https://github.com/django/django) from 4.0.4 to 4.0.6.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@4.0.4...4.0.6)

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

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