Revert "Use fallback approach for nested matmul (#85311)"
This reverts commit 7c31f6e67213cbe773b0e2556f880f6ce2449fc3.
Reverted https://github.com/pytorch/pytorch/pull/85311 on behalf of https://github.com/clee2000 due to broke lots of builds https://hud.pytorch.org/pytorch/pytorch/commit/7c31f6e67213cbe773b0e2556f880f6ce2449fc3 even though the pr was green
