Align more metadata with other repo types (models,spaces)

[julien-c]

see also associated PR on the datasets-tagging Space: https://huggingface.co/spaces/huggingface/datasets-tagging/discussions/2 (to merge after this one is merged)

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[lhoestq]

I just set a default value (None) for the deprecated licenses and languages fields, which should fix most of the CI failures.

Note that the CI should still be red because you edited many dataset cards and they're still missing some content - but this is unrelated to this PR so we can ignore these failures

[julien-c]

thanks so much @lhoestq !!

[lhoestq]

It looks all good thanks :)

The 345 CI failures are all unrelated to this PR (bad/missing tags or content in dataset cards)

Can you check that it looks good to you @albertvillanova ?

[albertvillanova]

Thank you @julien-c, really necessary to align as much as possible all projects.

Indeed I had already noticed that when creating a new dataset using the Hub UI, if a license was chosen from the dropdown menu, the generated tag was license instead of licenses. This fixes this issue as well.

[julien-c]

There's also a follow-up PR to this one, in #4613 – I would suggest to merge all of them at the same time and hope not too many things are broken 🙀 🙀

[lhoestq]

Alright merging this one now, let's see how broken things get