Fix typo in Etherscan API key env field (should match .env.example)

Author: lukaw3d

packages/nextjs/utils/scaffold-eth/networks.ts

@@ -43,7 +43,7 @@ export const getAlchemyHttpUrl = (chainId: number) => {
     : undefined;
 };
 
-const MAINNET_ETHERSCAN_API_KEY = process.env.NEXT_PUBLIC_ETHERSCAN_API_KEY || "DNXJA8RX2Q3VZ4URQIWP7Z68CJXQZSC6AW";
+const MAINNET_ETHERSCAN_API_KEY = process.env.NEXT_PUBLIC_MAINNET_ETHERSCAN_API_KEY || "DNXJA8RX2Q3VZ4URQIWP7Z68CJXQZSC6AW";
 const OPTIMISM_ETHERSCAN_API_KEY = process.env.NEXT_PUBLIC_OPTIMISM_ETHERSCAN_API_KEY || "";
 const POLYGON_ETHERSCAN_API_KEY = process.env.NEXT_PUBLIC_POLYGON_ETHERSCAN_API_KEY || "";
 const ARBITRUM_ETHERSCAN_API_KEY = process.env.NEXT_PUBLIC_ARBITRUM_ETHERSCAN_API_KEY || "";