build(deps-dev): bump fastify from 3.29.1 to 4.20.0

Bumps [fastify](https://github.com/fastify/fastify) from 3.29.1 to 4.20.0.
- [Release notes](https://github.com/fastify/fastify/releases)
- [Commits](fastify/fastify@v3.29.1...v4.20.0)

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

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