fix Typo: "merkelRoot" -> "merkleRoot"
fix Typo: "merkelRoot" -> "merkleRoot"


Former-commit-id: 0432b245264163908db11262d59622312db4ee1c
syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin