[docs] fix comment: the return value of findFork is _not_ an ancestor when the specified block is on the active chain
[docs] fix comment: the return value of findFork is _not_ an ancestor when the specified block is on the active chain

update with suggested comment text from the reviewers

DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin,peercoin/peercoin,peercoin/peercoin,DigitalPandacoin/pandacoin,peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,peercoin/peercoin,DigitalPandacoin/pandacoin,DigitalPandacoin/pandacoin