chore(deps): bump ajv and @asyncapi/modelina in /modelina-cli (#2173)

Bumps [ajv](https://github.com/ajv-validator/ajv) to 6.12.6 and updates ancestor dependency [@asyncapi/modelina](https://github.com/asyncapi/modelina). These dependencies need to be updated together.


Updates `ajv` from 5.5.2 to 6.12.6
- [Release notes](https://github.com/ajv-validator/ajv/releases)
- [Commits](ajv-validator/ajv@v5.5.2...v6.12.6)

Updates `@asyncapi/modelina` from 4.0.0-next.64 to 4.0.0
- [Release notes](https://github.com/asyncapi/modelina/releases)
- [Changelog](https://github.com/asyncapi/modelina/blob/master/.releaserc)
- [Commits](v4.0.0-next.64...v4.0.0)

---
updated-dependencies:
- dependency-name: ajv
  dependency-type: indirect
- dependency-name: "@asyncapi/modelina"
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: asyncapi-bot-eve <[email protected]>