Control.Lens.Traversal: fix doctest for failover
Control.Lens.Traversal: fix doctest for failover

omefire/lens,Icelandjack/lens,timjb/lens,cdepillabout/lens,Gabriel439/lens,hvr/lens,danidiaz/lens,rpglover64/lens,Fuuzetsu/lens,hvr/lens,cchalmers/lens,ddssff/lens