fix(c4-117-g11): using > 0 costs more gas than != 0 when used on a uint in a require()

Signed-off-by: Tomás Migone <[email protected]>

Author: tmigone

contracts/gateway/L1GraphTokenGateway.sol

@@ -203,7 +203,7 @@ contract L1GraphTokenGateway is Initializable, GraphTokenGateway, L1ArbitrumMess
     ) external payable override notPaused returns (bytes memory) {
         IGraphToken token = graphToken();
         require(_l1Token == address(token), "TOKEN_NOT_GRT");
-        require(_amount > 0, "INVALID_ZERO_AMOUNT");
+        require(_amount != 0, "INVALID_ZERO_AMOUNT");
         require(_to != address(0), "INVALID_DESTINATION");
 
         // nested scopes to avoid stack too deep errors

contracts/l2/gateway/L2GraphTokenGateway.sol

@@ -143,7 +143,7 @@ contract L2GraphTokenGateway is GraphTokenGateway, L2ArbitrumMessenger, Reentran
         bytes calldata _data
     ) public payable override notPaused nonReentrant returns (bytes memory) {
         require(_l1Token == l1GRT, "TOKEN_NOT_GRT");
-        require(_amount > 0, "INVALID_ZERO_AMOUNT");
+        require(_amount != 0, "INVALID_ZERO_AMOUNT");
         require(msg.value == 0, "INVALID_NONZERO_VALUE");
         require(_to != address(0), "INVALID_DESTINATION");