Fix import: use EIP712 instead of incorrect ERC712

Author: pky1987

src/MerkleAirdrop.sol

@@ -4,7 +4,7 @@ pragma solidity ^0.8.24;
 
 import {MerkleProof} from "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
 import {IERC20, SafeERC20} from "@openzeppelin/contracts/token/ERC20/utils/SafeERC20.sol";
-import {ERC712} from "@openzeppelin/contracts/utils/cryptography/EIP712.sol";
+import {EIP712} from "@openzeppelin/contracts/utils/cryptography/EIP712.sol";
 import {SignatureChecker} from "@openzeppelin/contracts/utils/cryptography/SignatureChecker.sol";
 import {ECDSA} from "@openzeppelin/contracts/utils/cryptography/ECDSA.sol";
 import {MessageHashUtils} from "@openzeppelin/contracts/utils/cryptography/MessageHashUtils.sol";