Fix the fsdp config cannot work issue.
Author: yuanwu2017
Pull request: yes

# What does this PR do?
The fsdp config generated by accelerate config is all fsdp prefixed. If passed in as parameters, these parameters will not work. But passing in in the fsdp_config.json method, these parameters can work. This patch makes them behave consistently and can work.


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Fixes # (issue)


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cc @SunMarc 

@ArthurZucker Please help to review.

> Thanks, just a nit. Can you also add a small test ?

Done.
`pytest tests/fsdp/test_fsdp.py`
<img width="778" alt="image" src="https://github.com/user-attachments/assets/7d279584-8dbb-44fd-9045-2275acd395ea" />


Thanks for adding the test. Just a minor nit, please do `make style` to fix the CI also and we can merge

Done.

@Rocketknight1 @ArthurZucker Please help to review and merge.

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