Bump ajv from 6.12.6 to 8.12.0 in /graph-tutorial

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.12.6 to 8.12.0.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.12.6...v8.12.0)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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Author: dependabot[bot]