Update WikiANN data URL
MEMBER
We have to update the URL in the XTREME benchmark as well:

https://github.com/huggingface/datasets/blob/0dfc639cec450ed8762a997789a2ed63e63cdcf2/datasets/xtreme/xtreme.py#L411-L411


2021-07-26T09:34:03Z
https://github.com/huggingface/datasets/pull/2710#issuecomment-886541039
https://api.github.com/repos/huggingface/datasets/issues/2710
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2021-07-26T09:34:03Z
https://api.github.com/repos/huggingface/datasets/issues/comments/886541039
https://avatars.githubusercontent.com/u/42851186?v=4
https://api.github.com/users/lhoestq/events{/privacy}
https://api.github.com/users/lhoestq/followers
https://api.github.com/users/lhoestq/following{/other_user}
https://api.github.com/users/lhoestq/gists{/gist_id}
https://github.com/lhoestq
lhoestq
MDQ6VXNlcjQyODUxMTg2
https://api.github.com/users/lhoestq/orgs
https://api.github.com/users/lhoestq/received_events
https://api.github.com/users/lhoestq/repos
https://api.github.com/users/lhoestq/starred{/owner}{/repo}
https://api.github.com/users/lhoestq/subscriptions
User
https://api.github.com/users/lhoestq
public
WikiANN data source URL is no longer accessible: 404 error from Dropbox.

We have decided to host it at Hugging Face. This PR updates the data source URL, the metadata JSON file and the dataset card.

Close #2691.