Update url for conll2003
Following https://github.com/huggingface/datasets/issues/3582 I'm changing the download URL of the conll2003 data files, since the previous host doesn't have the authorization to redistribute the data
Hi. lhoestq 

![image](https://user-images.githubusercontent.com/21982975/150345097-154f2b1a-bb12-47af-bddf-40eec0a0dadb.png)
What is the solution for it?
you can see it is still doesn't work here.
https://colab.research.google.com/drive/1l52FGWuSaOaGYchit4CbmtUSuzNDx_Ok?usp=sharing
Thank you.
 For now you can specify `load_dataset(..., revision="master")` to use the fix on `master`.

We'll also do a new release of `datasets` tomorrow I think