Revert "Validate stock in OpticalItemStep."

This was actually the intended behaviour

This reverts commit 06ebfe036c06be9230e1c498aea7c1b8adbf5697

Change-Id: I3d8e085b0b1956aee2834c826759cfa3c6c6c16b
Merge "Revert "Validate stock in OpticalItemStep.""