Remove unused variables (#71)

Author: Mike-CZ

contracts/sfc/ConstantsManager.sol

@@ -32,19 +32,10 @@ contract ConstantsManager is Ownable {
     uint256 public targetGasPowerPerSecond;
     uint256 public gasPriceBalancingCounterweight;
 
-    address private secondaryOwner_erased;
-
-    //    event SecondaryOwnershipTransferred(address indexed previousOwner, address indexed newOwner);
-
     function initialize() external initializer {
         Ownable.initialize(msg.sender);
     }
 
-    //    function setSecondaryOwner(address v) onlyOwner external {
-    //        emit SecondaryOwnershipTransferred(secondaryOwner, v);
-    //        secondaryOwner = v;
-    //    }
-
     function updateMinSelfStake(uint256 v) external virtual onlyOwner {
         require(v >= 100000 * 1e18, "too small value");
         require(v <= 10000000 * 1e18, "too large value");

contracts/sfc/NodeDriver.sol

@@ -228,7 +228,6 @@ contract NodeDriverAuth is Initializable, Ownable {
 }
 
 contract NodeDriver is Initializable {
-    uint256 private erased0;
     NodeDriverAuth internal backend;
     EVMWriter internal evmWriter;
 

contracts/sfc/SFCState.sol

@@ -79,17 +79,11 @@ contract SFCState is Initializable, Ownable {
         uint256 totalSupply;
     }
 
-    uint256 private erased0;
     uint256 public totalSupply;
     mapping(uint256 => EpochSnapshot) public getEpochSnapshot;
 
-    uint256 private erased1;
-    uint256 private erased2;
-
     mapping(uint256 => uint256) public slashingRefundRatio; // validator ID -> (slashing refund ratio)
 
-    uint256 private erased3;
-    uint256 private erased4;
     uint256 public minGasPrice;
 
     address public treasuryAddress;