cnn_dailymail repeats itself
### Describe the bug

When I try to load `cnn_dailymail` dataset, it takes longer than usual and when I checked the dataset it's 3x bigger than it's supposed to be.

Check https://huggingface.co/datasets/cnn_dailymail: it says 287k rows for train. But when I check length of train split it says 861339.

Also I checked data:

```
>>> ds['train']['highlights'][0]                                           
"Harry Potter star Daniel Radcliffe gets £20M fortune as he turns 18 Monday . Young actor says he has no plans to fritter his cash away . Radcliffe's earnings from first five Potter films have been held in trust fund ."````

>>> ds['train']['highlights'][0]                                           
"Harry Potter star Daniel Radcliffe gets £20M fortune as he turns 18 Monday . Young actor says he has no plans to fritter his cash away . Radcliffe's earnings from first five Potter films have been held in trust fund ."````

>>> ds['train']['highlights'][287113]
"Harry Potter star Daniel Radcliffe gets £20M fortune as he turns 18 Monday .\nYoung actor says he has no plans to fritter his cash away .\nRadcliffe's earnings from first five Potter films have been held in trust fund ."````

>>> ds['train']['highlights'][574226]
"Harry Potter star Daniel Radcliffe gets £20M fortune as he turns 18 Monday .\nYoung actor says he has no plans to fritter his cash away .\nRadcliffe's earnings from first five Potter films have been held in trust fund ."
```

The datasets seems to be updated 6 days ago to convert it to Parquet. Probably, there is some issue with backward compatability.



### Steps to reproduce the bug

1.
```
from datasets import load_dataset
ds = load_dataset('cnn_dailymail', '3.0.0')
len(ds['train'])
```

### Expected behavior

It should not repeat itself.

### Environment info

datasets==2.13.2
Python==3.7.13