Fix markdown for Map and Set links (facebook#1011)

website/blog/2019-06-12-react-native-open-source-update.md

@@ -35,7 +35,7 @@ We’d like to highlight a number of recent contributions which we thought were
 
 The primary motivation of [Lean Core](https://github.com/react-native-community/discussions-and-proposals/issues/6) has been to split modules out of React Native into separate repositories so they can receive better maintenance. In just a six months repositories like [WebView](https://github.com/react-native-community/react-native-webview), [NetInfo](https://github.com/react-native-community/react-native-netinfo), [AsyncStorage](https://github.com/react-native-community/react-native-async-storage), the [website](https://github.com/facebook/react-native-website) and the [CLI](https://github.com/react-native-community/cli) received more than 800 Pull Requests combined. Besides better maintenance, these projects can also be independently released more often than React Native itself.
 
-We have also taken the opportunity to remove obsolete polyfills and legacy components from React Native itself. Polyfills were necessary in the past to support language features like `[Map](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map)` and `[Set](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set)` in older versions of JavaScriptCore (JSC). Now that React Native ships with a new version, these polyfills were removed.
+We have also taken the opportunity to remove obsolete polyfills and legacy components from React Native itself. Polyfills were necessary in the past to support language features like [`Map`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map) and [`Set`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set) in older versions of JavaScriptCore (JSC). Now that React Native ships with a new version, these polyfills were removed.
 
 This work is still in progress and many more things still need to be split out or removed both on the native and JavaScript side but there are early signs that we managed to reverse the trend of increasing the surface area and app size: When looking at the JavaScript bundle for example, about a year ago in version 0.54 the React Native JavaScript bundle size was 530kb and grew to 607kb (+77kb) by version 0.57 in just 6 months. Now we are seeing a bundle size reduction of 28kb down to 579kb on master, a delta of more than 100kb!