eth: nft bridge impl initialize

ethereum/contracts/nft/NFTBridgeImplementation.sol

@@ -15,6 +15,10 @@ contract NFTBridgeImplementation is NFTBridge {
         return tokenImplementation();
     }
 
+    function initialize() initializer public virtual {
+        // this function needs to be exposed for an upgrade to pass
+    }
+
     modifier initializer() {
         address impl = ERC1967Upgrade._getImplementation();
 

ethereum/contracts/nft/mock/MockNFTBridgeImplementation.sol

@@ -6,7 +6,7 @@ pragma solidity ^0.8.0;
 import "../NFTBridgeImplementation.sol";
 
 contract MockNFTBridgeImplementation is NFTBridgeImplementation {
-    function initialize() initializer public {
+    function initialize() initializer public override {
         // this function needs to be exposed for an upgrade to pass
     }