[`bnb`] Let's make the daily CI green 🍏 
# What does this PR do?

This PR fixes a test that is currently failing on the `main` branch.

Link to failing test: https://github.com/huggingface/transformers/actions/runs/4154270129/jobs/7186572507

Since the introduction of https://github.com/huggingface/transformers/pull/21524 - when loading `bigscience/bloom-1b7` it  detects `fp32` weights when using `torch_dtype="auto"`. Therefore the expected relative difference of the memory footprint is different than the expected one. 

This PR fixes the test by forcing `torch_dtype=torch.float16` when loading the fp16 model

cc @ydshieh @sgugger 
_The documentation is not available anymore as the PR was closed or merged._<|||||>Yeah I am unsure too, `auto` shold give `float16` according to the weights size: https://huggingface.co/bigscience/bloom-1b7/tree/main (1b7 parameters = 3.4GB in fp16)