Fix missing methods for Fuyu
Author: Isotr0py
Pull request: yes

# What does this PR do?

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This PR add missing methods in `modeling_fuyu.py` like `get_output_embeddings` etc.

## Before submitting
- [ ] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
- [x] Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/main/CONTRIBUTING.md#create-a-pull-request),
      Pull Request section?
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      [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/main/docs#writing-source-documentation).
- [ ] Did you write any new necessary tests?


## Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
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- text models: @ArthurZucker
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Comments:
cc @molbap