Revert "[quant][ao_migration] `torch.nn.quantized._reference` → `torch.ao.nn.quantized._reference` (#78715)"
This reverts commit a7344e52b9d746062923647ae00ca38578d272d4.
Reverted https://github.com/pytorch/pytorch/pull/78715 on behalf of https://github.com/janeyx99 due to sorry, reverting so https://github.com/pytorch/pytorch/pull/78713 could be cleanly reverted
