Removed repeated "To"

Summary:
Just a simple word repetition fix in docs.
Closes https://github.com/facebook/react-native/pull/7352

Differential Revision: D3257587

fb-gh-sync-id: a54f38f3bbed9b50cb9c1f8a35d5718bad3deb33
fbshipit-source-id: a54f38f3bbed9b50cb9c1f8a35d5718bad3deb33

docs/NativeModulesAndroid.md

@@ -317,7 +317,7 @@ componentWillMount: function() {
 
 ### Getting activity result from `startActivityForResult`
 
-You'll need to listen to `onActivityResult` if you want to get results from an activity you started with `startActivityForResult`. To to do this, the module must implement `ActivityEventListener`. Then, you need to register a listener in the module's constructor,
+You'll need to listen to `onActivityResult` if you want to get results from an activity you started with `startActivityForResult`. To do this, the module must implement `ActivityEventListener`. Then, you need to register a listener in the module's constructor,
 
 ```java
 reactContext.addActivityEventListener(this);