fix: mock counter version

Author: 0xrusowsky

test/mocks/MockCounter.sol

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: MIT
-pragma solidity ^0.8.13;
+pragma solidity >=0.6.0 <0.9.0;
 
 /// @notice Simple counter contract for testing multi-EVM deployments.
 contract MockCounter {