Updated inconsistent output in documentation examples for `ClassLabel`
Updated! 😄  The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/datasets/pr_7293). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update. @lhoestq, can you help with this failing test please? 🙏 
fix #7129 

@stevhliu