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().

Scoped to the call site added by this PR; the pre-existing ones in this file are
left to the file-wide migration.