Change Networking examples to use HTTPS.

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Closes https://github.com/facebook/react-native/pull/9388

Differential Revision: D3715004

fbshipit-source-id: c12abcdd54ae1176aaf666eed520b85e2f8db6bd

docs/Networking.md

@@ -48,7 +48,7 @@ Networking is an inherently asynchronous operation. Fetch methods will return a
 
   ```js
   getMoviesFromApiAsync() {
-    return fetch('http://facebook.github.io/react-native/movies.json')
+    return fetch('https://facebook.github.io/react-native/movies.json')
       .then((response) => response.json())
       .then((responseJson) => {
         return responseJson.movies;
@@ -64,7 +64,7 @@ You can also use the proposed ES2017 `async`/`await` syntax in a React Native ap
   ```js
   async getMoviesFromApi() {
     try {
-      let response = await fetch('http://facebook.github.io/react-native/movies.json');
+      let response = await fetch('https://facebook.github.io/react-native/movies.json');
       let responseJson = await response.json();
       return responseJson.movies;
     } catch(error) {