fixed one instance of 'train' to 'test'
Thanks ! good catch

Could you also update the metadata of this dataset ?
You can do so by running
```
datasets-cli test ./datasets/newsgroup --all_configs --save_infos --ignore_verifications
```
This should update the dataset_infos.json file that contains the size of all the splits for example. Hi,
`dataset_infos.json` should be updated now.

I believe this should be 'test' instead of 'train'