[fix]: iwslt2017 download urls
Hi ! Thanks for the fix ! Do you know where this new URL comes from ?

Also we try to not use Google Drive if possible, since it has download quota limitations. Do you know if the data is available from another host than Google Drive ? Oh, I found it just by following the link from the [IWSLT2017 homepage](https://wit3.fbk.eu/2017-01). Not sure if it's available from another host. Ok cool ! I guess it's ok to use this URL for now, and we can see later if we need to change it.

Before merging, could you update the `dataset_infos.json` file by running this command please ?
```
datasets-cli test ./datasets/iwslt2017 --save_infos --all_configs
``` sure thing. lmk if there's anything else i can do to help. just checking in. is there anything i can do to help on my end to get this merged? (the dummy data tests are failing due an incorrect path, i think)
Fixes #2076.