TST Fix PEFT integration test bitsandbytes config (#39082)
TST Fix PEFT integration test bitsandbytes config
The PEFT integration tests still used load_in_{4,8}_bit, which is
deprecated, moving to properly setting BitsAndBytesConfig. For 4bit,
also ensure that nf4 is being used to prevent
> RuntimeError: quant_type must be nf4 on CPU, got fp4
