fix: remove unused notFoundString prop

src/components/not-found.js

@@ -28,6 +28,5 @@ export default class NotFound extends React.PureComponent {
 
 NotFound.propTypes /* remove-proptypes */ = {
   notFound: PropTypes.func.isRequired,
-  notFoundString: PropTypes.string.isRequired,
   emojiProps: PropTypes.object.isRequired,
 }