remove occurence of deprecated url prop in readme (vercel#5786)

packages/next/README.md

@@ -624,7 +624,7 @@ Router.events.on('routeChangeError', (err, url) => {
 
 <p></p>
 
-Shallow routing allows you to change the URL without running `getInitialProps`. You'll receive the updated `pathname` and the `query` via the `url` prop of the same page that's loaded, without losing state.
+Shallow routing allows you to change the URL without running `getInitialProps`. You'll receive the updated `pathname` and the `query` via the `router` prop (injected using [`withRouter`](#using-a-higher-order-component)), without losing state.
 
 You can do this by invoking either `Router.push` or `Router.replace` with the `shallow: true` option. Here's an example: