Set scheduler_specific_kwargs to get_scheduler

[Uminosachi]

What does this PR do?

When setting the argument --lr_scheduler_type cosine_with_min_lr for python src/train.py, the following error occurs:

ValueError: One of min_lr or min_lr_rate should be set through the `lr_scheduler_kwargs`

In response, I provided the argument --lr_scheduler_kwargs '{"min_lr": 1e-7}', but an error still occurs because the scheduler_specific_kwargs argument is not properly passed to the get_scheduler function within the create_custom_scheduler function in src/llamafactory/train/utils.py.

To resolve this error, I have modified the code to set the scheduler_specific_kwargs argument to training_args.lr_scheduler_kwargs within the create_custom_scheduler function.

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[Uminosachi]

A TypeError may occur when handling string arguments if you are using a version of transformers prior to the following PR:

huggingface/transformers#30227

[hiyouga]

LGTM