build(deps): bump async and openapi-to-postmanv2 (#889)

Bumps [async](https://github.com/caolan/async) to 3.2.4 and updates ancestor dependency [openapi-to-postmanv2](https://github.com/postmanlabs/openapi-to-postman). These dependencies need to be updated together.


Updates `async` from 3.2.1 to 3.2.4
- [Release notes](https://github.com/caolan/async/releases)
- [Changelog](https://github.com/caolan/async/blob/master/CHANGELOG.md)
- [Commits](caolan/async@v3.2.1...v3.2.4)

Updates `openapi-to-postmanv2` from 4.0.0 to 4.21.0
- [Release notes](https://github.com/postmanlabs/openapi-to-postman/releases)
- [Changelog](https://github.com/postmanlabs/openapi-to-postman/blob/develop/CHANGELOG.md)
- [Commits](postmanlabs/openapi-to-postman@v4.0.0...v4.21.0)

---
updated-dependencies:
- dependency-name: async
  dependency-type: indirect
- dependency-name: openapi-to-postmanv2
  dependency-type: direct:development
...

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