fix(SimpleRegistry): adds ierc20 import to simple registry

Author: Alexangelj

contracts/test/SimpleRegistry.sol

@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 pragma solidity ^0.8.4;
 
+import "../interfaces/IERC20.sol";
 import "solmate/auth/Owned.sol";
 
 interface PortfolioLike {