Support streaming FLEURS dataset
## Dataset viewer issue for '*name of the dataset*'

https://huggingface.co/datasets/google/fleurs

```
Status code:   400
Exception:     NotImplementedError
Message:       Extraction protocol for TAR archives like 'https://storage.googleapis.com/xtreme_translations/FLEURS/af_za.tar.gz' is not implemented in streaming mode. Please use `dl_manager.iter_archive` instead.
```

Am I the one who added this dataset ? Yes

Can I fix this somehow in the script? @lhoestq @severo 
