[Whisper] Fix feature normalization in `WhisperFeatureExtractor`
Author: bofenghuang
Pull request: yes

# What does this PR do?

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Hello @ArthurZucker @sanchit-gandhi  ,

In this PR, I tried to fix the feature normalization in `WhisperFeatureExtractor` which is actually not used. The line 354 takes the `input_features` from the line 340.

In addition, the `zero_mean_unit_var_norm` expects a `padded_inputs["attention_mask"]` also in the sample level (48000) as `padded_inputs["input_features"]`. IMO it should not be rescaled in the line 344 (it's also repeated in the line 363).

Please let me know what you think :)

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Models:

- text models: @ArthurZucker and @younesbelkada
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Library:

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