Update pragma to 0.8.20 (#4489)

Co-authored-by: Francisco Giordano <fg@frang.io>
Co-authored-by: ernestognw <ernestognw@gmail.com>

contracts/token/ERC721/extensions/ERC721Enumerable.sol

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // OpenZeppelin Contracts (last updated v4.8.0) (token/ERC721/extensions/ERC721Enumerable.sol)
 
-pragma solidity ^0.8.19;
+pragma solidity ^0.8.20;
 
 import {ERC721} from "../ERC721.sol";
 import {IERC721Enumerable} from "./IERC721Enumerable.sol";