ExpectedMoreSplits error when loading C4 dataset
### Describe the bug

I encounter bug when running the example command line 

```python
    python main.py \
    --model decapoda-research/llama-7b-hf \
    --prune_method wanda \
    --sparsity_ratio 0.5 \
    --sparsity_type unstructured \
    --save out/llama_7b/unstructured/wanda/ 
```

The bug occurred at these lines of code (when loading c4 dataset) 

```python
traindata = load_dataset('allenai/c4', 'allenai--c4', data_files={'train': 'en/c4-train.00000-of-01024.json.gz'}, split='train')
valdata = load_dataset('allenai/c4', 'allenai--c4', data_files={'validation': 'en/c4-validation.00000-of-00008.json.gz'}, split='validation')
```

The error message states:
```    
raise ExpectedMoreSplits(str(set(expected_splits) - set(recorded_splits)))                                                                           
datasets.utils.info_utils.ExpectedMoreSplits: {'validation'}
```



### Steps to reproduce the bug

1. I encounter bug when running the example command line 


### Expected behavior

The error message states:
```    
raise ExpectedMoreSplits(str(set(expected_splits) - set(recorded_splits)))                                                                           
datasets.utils.info_utils.ExpectedMoreSplits: {'validation'}
```



### Environment info

I'm using cuda 12.4, so I use ```pip install pytorch``` instead of conda provided in install.md

Also, I've tried another environment using the same commands in install.md, but the same bug occured 