doc: Remove mention of renamed mapBlocksUnlinked
doc: Remove mention of renamed mapBlocksUnlinked

Former-commit-id: 039c75c805247c4d40842275ca50dbbab006a5fc
syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin2,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin