Bump ajv and serve

Bumps [ajv](https://github.com/ajv-validator/ajv) to 6.12.4 and updates ancestor dependency [serve](https://github.com/vercel/serve). These dependencies need to be updated together.


Updates `ajv` from 6.5.3 to 6.12.4
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.5.3...v6.12.4)

Updates `serve` from 11.3.2 to 14.1.1
- [Release notes](https://github.com/vercel/serve/releases)
- [Commits](vercel/serve@11.3.2...14.1.1)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: indirect
- dependency-name: serve
  dependency-type: direct:development
...

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Author: dependabot[bot]