Update IntegrationWithExistingApps.md

Summary:
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> **Unless you are a React Native release maintainer and cherry-picking an *existing* commit into a current release, ensure your pull request is targeting the `master` React Native branch.**

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Closes https://github.com/facebook/react-native/pull/8869

Differential Revision: D3580218

Pulled By: JoelMarcey

fbshipit-source-id: 9f71825ed0a63739497ec7fa77081df0a72b6747

docs/IntegrationWithExistingApps.md

@@ -348,7 +348,7 @@ AppRegistry.registerComponent('RNHighScores', () => RNHighScores);
 
 ## The Magic: `RCTRootView`
 
-Now that your React Native component is created via `index.ios.js`, you need to add that component to a new or existing `ViewController`. The easiest path is to take is to optionally create an event path to your component and then add that component to an existing `ViewController`.
+Now that your React Native component is created via `index.ios.js`, you need to add that component to a new or existing `ViewController`. The easiest path to take is to optionally create an event path to your component and then add that component to an existing `ViewController`.
 
 We will tie our React Native component with a new native view in the `ViewController` that will actually host it called `RCTRootView` .