Revert "RowwiseMoments: use float as acc type for bfloat16 inputs (#81850)"
This reverts commit 2fe3ea65c2b9147077ea3a3dc4757f1768483ba4.
Reverted https://github.com/pytorch/pytorch/pull/81850 on behalf of https://github.com/malfet due to Revert as caused perf regression, see https://github.com/pytorch/benchmark/issues/1099
