Bump fastify and netlify-cli

Removes [fastify](https://github.com/fastify/fastify). It's no longer used after updating ancestor dependency [netlify-cli](https://github.com/netlify/cli). These dependencies need to be updated together.


Removes `fastify`

Updates `netlify-cli` from 18.1.0 to 21.5.0
- [Release notes](https://github.com/netlify/cli/releases)
- [Changelog](https://github.com/netlify/cli/blob/main/CHANGELOG.md)
- [Commits](netlify/cli@v18.1.0...v21.5.0)

---
updated-dependencies:
- dependency-name: fastify
  dependency-version: 
  dependency-type: indirect
- dependency-name: netlify-cli
  dependency-version: 21.5.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]