Merge pull request #4881 from ethereum-optimism/ctb/mintable-721-version

contracts-bedrock: be explicit with mintable erc721 token version

integration-tests/hardhat.config.ts

@@ -39,6 +39,20 @@ const config: HardhatUserConfig = {
           },
         },
       },
+      {
+        version: '0.8.15',
+        settings: {
+          optimizer: { enabled: true, runs: 200 },
+          metadata: {
+            bytecodeHash: 'none',
+          },
+          outputSelection: {
+            '*': {
+              '*': ['storageLayout'],
+            },
+          },
+        },
+      },
     ],
   },
   gasReporter: {

packages/contracts-bedrock/contracts/universal/OptimismMintableERC721.sol

 // SPDX-License-Identifier: MIT
-pragma solidity ^0.8.0;
+pragma solidity 0.8.15;
 
 import {
     ERC721Enumerable