Revert "Update test/token/ERC20/extensions/ERC4626.t.sol"

This reverts commit 99a220c.

Author: daejunpark

test/token/ERC20/extensions/ERC4626.t.sol

@@ -8,7 +8,7 @@ import {ERC4626Mock, IERC20Metadata} from "../../../../contracts/mocks/ERC4626Mo
 
 contract ERC4626StdTest is ERC4626Test {
     function setUp() public override {
-        _underlying_ = address(new ERC20Mock("MockERC20", "MockERC20", address(0), 0));
+        _underlying_ = address(new ERC20Mock("MockERC20", "MockERC20", address(this), 0));
         _vault_ = address(new ERC4626Mock(IERC20Metadata(_underlying_), "MockERC4626", "MockERC4626"));
         _delta_ = 0;
         _vaultMayBeEmpty = false;