Bump django-grappelli from 3.0.6 to 3.0.8

Bumps [django-grappelli](https://github.com/sehmaschine/django-grappelli) from 3.0.6 to 3.0.8.
- [Changelog](https://github.com/sehmaschine/django-grappelli/blob/master/docs/changelog.rst)
- [Commits](sehmaschine/django-grappelli@3.0.6...3.0.8)

---
updated-dependencies:
- dependency-name: django-grappelli
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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