Bump cynic from 3.4.3 to 3.5.1 in /backend

Bumps [cynic](https://github.com/obmarg/cynic) from 3.4.3 to 3.5.1.
- [Release notes](https://github.com/obmarg/cynic/releases)
- [Changelog](https://github.com/obmarg/cynic/blob/main/CHANGELOG.md)
- [Commits](obmarg/cynic@v3.4.3...v3.5.1)

---
updated-dependencies:
- dependency-name: cynic
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]