compatibility patch for BnB >=0.46

[Borda]

Bug description

see update for litGPT:

• CI job: https://dev.azure.com/Lightning-AI/lit%20Models/_build/results?buildId=236175&view=logs&j=47e66f3c-897a-5428-da11-bf5c7745762e&t=4e34480b-1ce5-584a-e5a7-81585edd72ef&l=656
• bump PR: build(deps): update bitsandbytes requirement from <0.43,>=0.42 to >=0.42,<0.47 litgpt#2069

What version are you seeing the problem on?

v2.5

Reproduced in studio

No response

How to reproduce the bug

This is not the right way:

            if hasattr(bnb.functional, "double_quant"):
                CB, _, SCB, _, _ = bnb.functional.double_quant(B)
            else:  # for bitsandbytes versions ≥0.46
>               CB, SCB = bnb.functional.int8_double_quant(B)
E               ValueError: too many values to unpack (expected 2)

Error messages and logs

# Error messages and logs here please

Environment

Current environment

#- PyTorch Lightning Version (e.g., 2.5.0):
#- PyTorch Version (e.g., 2.5):
#- Python version (e.g., 3.12):
#- OS (e.g., Linux):
#- CUDA/cuDNN version:
#- GPU models and configuration:
#- How you installed Lightning(`conda`, `pip`, source):

More info

No response

cc @Borda