Possible redundant code in proof reconstruction

[Guillaume Ballet]

From @jsign in #384 :

I still feel this if is a bit strange. We're reconstructing the values to be assigned in the leaf when we'll soon create the LeafNode.

But see what we do in CreatePath(...):

• We use that value slice as expected.
• We do some extra assignments from stemInfo.

Is the latter needed? Or a noop? Or maybe I'm missing something.

This looks like leftover code from a previous version of the tree API. I didn't want to remove it just yet, but it looks like this is redundant.