accumulator/utils: remove unused function subTreePositions

This function hasn't been used since commit
e83f377. It seems that it was
only useful for removev2 and earlier, i.e. it makes sense to get
rid of it.

accumulator/utils.go

@@ -394,40 +394,6 @@ func getRootsForwards(leaves uint64, forestRows uint8, roots *[]uint64) []uint8
 	return rows
 }
 
-// subTreePositions takes in a node position and forestRows and returns the
-// positions of all children that need to move AND THE NODE ITSELF.  (it works
-// nicer that way)
-// Also it returns where they should move to, given the destination of the
-// sub-tree root.
-// can also be used with the "to" return discarded to just enumerate a subtree
-// swap tells whether to activate the sibling swap to try to preserve order
-func subTreePositions(
-	subroot uint64, moveTo uint64, forestRows uint8) (as []arrow) {
-
-	subRow := detectRow(subroot, forestRows)
-	//	fmt.Printf("node %d row %d\n", subroot, subRow)
-	rootDelta := int64(moveTo) - int64(subroot)
-	// do this with nested loops instead of recursion ... because that's
-	// more fun.
-	// r is out row in the forest
-	// start at the bottom and ascend
-	for r := uint8(0); r <= subRow; r++ {
-		// find leftmost child on this row; also calculate the
-		// delta (movement) for this row
-		depth := subRow - r
-		leftmost := childMany(subroot, depth, forestRows)
-		rowDelta := rootDelta << depth // usually negative
-		for i := uint64(0); i < 1<<depth; i++ {
-			// loop left to right
-			f := leftmost + i
-			t := uint64(int64(f) + rowDelta)
-			as = append(as, arrow{from: f, to: t})
-		}
-	}
-
-	return
-}
-
 // TODO: unused? useless?
 // subTreeLeafRange gives the range of leaves under a node
 func subTreeLeafRange(