build(deps): bump celery from 4.4.7 to 5.0.0 in /src/karmen_backend

Bumps [celery](https://github.com/celery/celery) from 4.4.7 to 5.0.0.
- [Release notes](https://github.com/celery/celery/releases)
- [Changelog](https://github.com/celery/celery/blob/master/Changelog.rst)
- [Commits](celery/celery@v4.4.7...v5.0.0)

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