[dtype] Make learn_rounding_digits() work with new pandas dtypes

[R-Palazzo]

Problem Description

Currently, learn_rounding_digits() crashes with the new pandas dtypes on python 3.8. Running this code:

import pandas as pd
from rdt.transformers.utils import learn_rounding_digits

data = pd.Series([1.1, 2.2, 3.3], dtype='Float64')

learn_rounding_digits(data)

Raises the following error:
TypeError: ufunc 'isinf' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''

Expected behavior

The method should work with any numerical dtype on every python version.