fix: whitelist to allowlist

Signed-off-by: Tomás Migone <tomas@edgeandnode.com>

Author: tmigone

contracts/gateway/ICallhookReceiver.sol

@@ -3,7 +3,7 @@
 /**
  * @title Interface for contracts that can receive callhooks through the Arbitrum GRT bridge
  * @dev Any contract that can receive a callhook on L2, sent through the bridge from L1, must
- * be whitelisted by the governor, but also implement this interface that contains
+ * be allowlisted by the governor, but also implement this interface that contains
  * the function that will actually be called by the L2GraphTokenGateway.
  */
 pragma solidity ^0.7.6;