<br /> doesn't exist in React Native

Summary:
Replace `<br />` with `{'\n'}` in order to provide an example of working line breaks in React Native.
Closes https://github.com/facebook/react-native/pull/10323

Differential Revision: D3995544

Pulled By: JoelMarcey

fbshipit-source-id: 8404db8f23eeb606a5a5ed98ca1b7f9b20917e46

Libraries/Text/Text.js

@@ -65,7 +65,7 @@ const viewConfig = {
  *     return (
  *       <Text style={styles.baseText}>
  *         <Text style={styles.titleText} onPress={this.onPressTitle}>
- *           {this.state.titleText}<br /><br />
+ *           {this.state.titleText}{'\n'}{'\n'}
  *         </Text>
  *         <Text numberOfLines={5}>
  *           {this.state.bodyText}