Formatting fixes

Summary:
What existing problem does the pull request solve?
It fixes some formatting issues that appear in the React Native documentation.

**Test plan**
Run the documentation extraction and verify the content appears correctly as `code` formatted sections.
Closes https://github.com/facebook/react-native/pull/12346

Differential Revision: D4553340

Pulled By: hramos

fbshipit-source-id: b8307b3c3e1c3451f740c46222e10ec3c45e3008

Libraries/Text/Text.js

@@ -139,13 +139,13 @@ const Text = React.createClass({
     /**
      * This function is called on press.
      *
-     * e.g., `onPress={() => console.log('1st')}``
+     * e.g., `onPress={() => console.log('1st')}`
      */
     onPress: PropTypes.func,
     /**
      * This function is called on long press.
      *
-     * e.g., `onLongPress={this.increaseSize}>``
+     * e.g., `onLongPress={this.increaseSize}>`
      */
     onLongPress: PropTypes.func,
     /**