Build(deps): Bump ajv from 6.9.1 to 6.12.3

Bumps [ajv](https://github.com/ajv-validator/ajv) from 6.9.1 to 6.12.3.
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v6.9.1...v6.12.3)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: indirect
...

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

Author: dependabot[bot]