build(deps-dev): bump @openapitools/openapi-generator-cli

Bumps [@openapitools/openapi-generator-cli](https://github.com/OpenAPITools/openapi-generator-cli) from 2.20.2 to 2.21.4.
- [Release notes](https://github.com/OpenAPITools/openapi-generator-cli/releases)
- [Changelog](https://github.com/OpenAPITools/openapi-generator-cli/blob/master/.releaserc)
- [Commits](OpenAPITools/openapi-generator-cli@v2.20.2...v2.21.4)

---
updated-dependencies:
- dependency-name: "@openapitools/openapi-generator-cli"
  dependency-version: 2.21.4
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]