Removed Parse reference since its service is shutting down

Summary:I updated the Network documentation to not lead users to use Parse, since its service is shutting down.
Closes https://github.com/facebook/react-native/pull/6140

Differential Revision: D2974665

fb-gh-sync-id: 2a784ad00f742f9f2e2ce369f8b3e1eaab0e2ad4
shipit-source-id: 2a784ad00f742f9f2e2ce369f8b3e1eaab0e2ad4

docs/Network.md

@@ -52,7 +52,7 @@ fetch('https://mywebsite.com/endpoint/', {
     });
   ```
 2.  Called within an asynchronous function using ES7 `async`/`await` syntax:
-  
+
   ```js
   class MyComponent extends React.Component {
     ...
@@ -124,4 +124,4 @@ request.send();
 
 Please follow the [MDN Documentation](https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest) for a complete description of the API.
 
-As a developer, you're probably not going to use XMLHttpRequest directly as its API is very tedious to work with. But the fact that it is implemented and compatible with the browser API gives you the ability to use third-party libraries such as [Parse](https://parse.com/products/javascript), [frisbee](https://github.com/niftylettuce/frisbee), or [axios](https://github.com/mzabriskie/axios) directly from npm.
+As a developer, you're probably not going to use XMLHttpRequest directly as its API is very tedious to work with. But the fact that it is implemented and compatible with the browser API gives you the ability to use third-party libraries such as [frisbee](https://github.com/niftylettuce/frisbee) or [axios](https://github.com/mzabriskie/axios) directly from npm.