remove openapi-spec-validator (use spectral)
because I like these stats:

<img width="135" alt="Capture d’écran 2024-03-12 à 01 22 19" src="https://github.com/huggingface/datasets-server/assets/1676121/81b79030-4276-458d-bf43-72cbdd61d3ef">

remove openapi-spec-validator (use spectral): because I like these stats:

<img width="135" alt="Capture d’écran 2024-03-12 à 01 22 19" src="https://github.com/huggingface/datasets-server/assets/1676121/81b79030-4276-458d-bf43-72cbdd61d3ef">
