Inline keccak256 result (#1741)
Inline keccak256 result (#1741)

* inline keccak256 result

* Update ERC777.sol

* switch hex constant style

* Update ERC777.sol

(cherry picked from commit e60c7904d4d205137969efc2b5cf48670a422c6e)

OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zeppelin-solidity,OpenZeppelin/zeppelin-solidity,OpenZeppelin/openzeppelin-contracts,OpenZeppelin/zep-solidity,OpenZeppelin/zep-solidity,OpenZeppelin/openzeppelin-contracts