I think there's an important distinction that needs to be made here based on the other conversation: a potion of healing will prevent scarring for a wound that it heals, but it won't remove an already-existing scar. Otherwise you wouldn't have burly scarred warriors adventuring all over the place.

And if it can't do that, let alone restore lost limbs, I doubt it could undo circumcision. That said, I'm sure a potion that could do so can be researched without too much trouble.