Bump @ckeditor/ckeditor5-build-balloon from 12.4.0 to 15.0.0

Bumps [@ckeditor/ckeditor5-build-balloon](https://github.com/ckeditor/ckeditor5-build-balloon) from 12.4.0 to 15.0.0.
- [Release notes](https://github.com/ckeditor/ckeditor5-build-balloon/releases)
- [Changelog](https://github.com/ckeditor/ckeditor5-build-balloon/blob/master/CHANGELOG.md)
- [Commits](https://github.com/ckeditor/ckeditor5-build-balloon/compare/v12.4.0...v15.0.0

)

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