Is dataset timit_asr broken?
Hi,

thanks for the report, but this is a duplicate of #2052.  @mariosasko 
Thank you for your quick response! Following #2052, I've fixed the problem.
Using `timit_asr` dataset, I saw all records are the same.

``` python
from datasets import load_dataset, load_metric

timit = load_dataset("timit_asr")

from datasets import ClassLabel
import random
import pandas as pd
from IPython.display import display, HTML

def show_random_elements(dataset, num_examples=10):
    assert num_examples <= len(dataset), "Can't pick more elements than there are in the dataset."
    picks = []
    for _ in range(num_examples):
        pick = random.randint(0, len(dataset)-1)
        while pick in picks:
            pick = random.randint(0, len(dataset)-1)
        picks.append(pick)

    df = pd.DataFrame(dataset[picks])
    display(HTML(df.to_html()))


show_random_elements(timit['train'].remove_columns(["file", "phonetic_detail", "word_detail", "dialect_region", "id", 
                                                    "sentence_type", "speaker_id"]), num_examples=20)

```

`output`

<img width="312" alt="Screen Shot 2021-03-28 at 17 29 04" src="https://user-images.githubusercontent.com/42398050/112746646-21acee80-8feb-11eb-84f3-dbb5d4269724.png">


I double-checked it [here](https://huggingface.co/datasets/viewer/), and met the same problem.

<img width="1374" alt="Screen Shot 2021-03-28 at 17 32 07" src="https://user-images.githubusercontent.com/42398050/112746698-9bdd7300-8feb-11eb-97ed-5babead385f4.png">
