Dataset preview rounds numbers
When previewing a dataset using the dataset viewer, e.g. : https://huggingface.co/datasets/sasha/real_toxicity_prompts

Values close to 1 (e.g. 0.9999) are rounded up in the UI, which is a bit confusing.

@lhoestq proposed that maybe the function to use here would be `floor(value)`, not `round(value)` 

For reference, the original dataset is:
![image](https://user-images.githubusercontent.com/14205986/177581736-84d28059-cb1d-4d8e-b572-842fc6689d4a.png)

Dataset preview rounds numbers: When previewing a dataset using the dataset viewer, e.g. : https://huggingface.co/datasets/sasha/real_toxicity_prompts

Values close to 1 (e.g. 0.9999) are rounded up in the UI, which is a bit confusing.

@lhoestq proposed that maybe the function to use here would be `floor(value)`, not `round(value)` 

For reference, the original dataset is:
![image](https://user-images.githubusercontent.com/14205986/177581736-84d28059-cb1d-4d8e-b572-842fc6689d4a.png)
