randomNetLatticeCreate(): oppEdge is identical to edge — duplicate detection for undirected edges is broken

[oxy86]

In graph_random_networks.cpp, both edge and oppEdge are constructed as i + "<->" + target. The intended reverse edge target + "<->" + i is never checked, so the duplicate guard !latticeEdges.contains(oppEdge) is always redundant with !latticeEdges.contains(edge). This may result in duplicate edges being added to the lattice.