Update SafeERC20.sol (#1693)

contracts/token/ERC20/SafeERC20.sol

@@ -45,7 +45,7 @@ library SafeERC20 {
 
     /**
      * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
-     * on the return value: the return value is optional (but if data is returned, it must equal true).
+     * on the return value: the return value is optional (but if data is returned, it must not be false).
      * @param token The token targeted by the call.
      * @param data The call data (encoded using abi.encode or one of its variants).
      */