Update docs

contracts/proxy/utils/UUPSUpgradeable.sol

@@ -15,6 +15,8 @@ import {ERC1967Utils} from "../ERC1967/ERC1967Utils.sol";
  * `UUPSUpgradeable` with a custom implementation of upgrades.
  *
  * The {_authorizeUpgrade} function must be overridden to include access restriction to the upgrade mechanism.
+ *
+ * @custom:stateless
  */
 abstract contract UUPSUpgradeable is IERC1822Proxiable {
     /// @custom:oz-upgrades-unsafe-allow state-variable-immutable