Bump jsonschema from 3.2.0 to 4.20.0 in /backend

Bumps [jsonschema](https://github.com/python-jsonschema/jsonschema) from 3.2.0 to 4.20.0.
- [Release notes](https://github.com/python-jsonschema/jsonschema/releases)
- [Changelog](https://github.com/python-jsonschema/jsonschema/blob/main/CHANGELOG.rst)
- [Commits](python-jsonschema/jsonschema@v3.2.0...v4.20.0)

---
updated-dependencies:
- dependency-name: jsonschema
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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