Revert "Horizontally fuse input concatenation (#108115)"
This reverts commit 5911faeb8fc3f625f9c3a42e58d45f7b7578ab8a.
Reverted https://github.com/pytorch/pytorch/pull/108115 on behalf of https://github.com/osalpekar due to Broke internal benchmarking job. See [D48890838](https://www.internalfb.com/diff/D48890838) ([comment](https://github.com/pytorch/pytorch/pull/108115#issuecomment-1703546520))
