Per review feedback, replace the torchao.utils.get_current_accelerator_device()
helper with the upstream torch.accelerator.current_accelerator() API, which is
the direction tracked in #2917 / #4384.

Note the suggested spelling in the review comment,
torch.accelerator.get_current_accelerator(), does not exist; the actual API is
torch.accelerator.current_accelerator().

This also drops the torchao.utils import that the previous commit added, since
it would otherwise be unused (ruff F401).