🚨🚨🚨  Fix rescale ViVit Efficientnet
# What does this PR do?

Fixes the rescaling logic for both EffiicentNet and ViVit. 

EfficientNet: The values were being rescale between [-0.5, 0.5] 

ViVit: values were being rescale between [-7.689350249903882e-06, 0.9999923106497501] as scale was being treated as having a value 255 in the `rescale` method, rather than 1/255. 

**This is a breaking change** and will affect the model outputs for both these models. However, it is a bug fix and should improve model predictions. 

## Before submitting
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- [x] Did you write any new necessary tests?
_The documentation is not available anymore as the PR was closed or merged._<|||||>If I'm not mistaken this PR is problematic as it breaks the `rescale` function. If I rebase my PR https://github.com/huggingface/transformers/pull/24796 to `main` the torchvision transforms vs transformers image transforms equivalency test fails: `tests/models/idefics/test_image_processing_idefics.py::IdeficsImageProcessingTest::test_torchvision_numpy_transforms_equivalency`