Fix language and license tag names in all Hub datasets
While working on this:
- #5137

we realized there are still many datasets with deprecated "languages" and "licenses" tag names (instead of "language" and "license").

This is a blocking issue: no subsequent PR can be opened to modify their metadata: a ValueError will be thrown.

We should fix the "language" and "license" tag names in all Hub datasets.

TODO:
- [x] Fix language and license tag names in 402 Hub datasets

CC: @julien-c 