Remove Optional[PILImageResampling] typing
# What does this PR do?

Resolves bug if Pillow < 2.9.1 resulting from type checks. If lower versions of Pillow are used, `PILImageResampling` is an alias for the `PIL.Image` module c.f. [definition here](https://github.com/huggingface/transformers/blob/d3c05666798bd8fcc7a03564436e5100b080a5df/src/transformers/image_utils.py#L48). When defining`var: Optional[obj] = None` - specified `obj` in `Optional` can't be a module - so it fails e.g. [here](https://github.com/huggingface/transformers/blob/d3c05666798bd8fcc7a03564436e5100b080a5df/src/transformers/models/segformer/image_processing_segformer.py#L231). 

The PR also replaces any remaining `PIL.Image.Resampling` with `PILImageResampling` in the codebase. 

Another option is to define a new type. I decided to go for the fastest resolution - LMK if you think this is better. 


## Before submitting
- [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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      Pull Request section?
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      to it if that's the case.
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      [documentation guidelines](https://github.com/huggingface/transformers/tree/main/docs), and
      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


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