in peft finetune, only the trainable parameters need to be saved
Author: sywangyi
Pull request: yes

to reduce the storage size and also save the time of checkpoint saving while using deepspeed for training

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Comments:
@younesbelkada @pacman100 please help review the PR.

@sywangyi can you try to merge your branch with upstream main? Perhaps it will fix the current failing CI

@younesbelkada I have rebased to main. the code quality check failure is not related with the PR

@sywangyi can you try to re-run `make fixup` with `pip uninstall black && pip install -U ruff==0.1.5` ?

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_27825). All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

@pacman100 could you help review the PR? Thanks.