Remove no longer used prop from example

Author: xiaolin

example/app.js

@@ -314,14 +314,6 @@ class App extends React.Component {
                   checked={this.state.showIndex}/>
                   <label htmlFor='show_index'>show index</label>
               </li>
-              <li>
-                <input
-                  id='slide_on_thumbnail_hover'
-                  type='checkbox'
-                  onChange={this._handleCheckboxChange.bind(this, 'slideOnThumbnailHover')}
-                  checked={this.state.slideOnThumbnailHover}/>
-                  <label htmlFor='slide_on_thumbnail_hover'>slide on thumbnail hover (desktop)</label>
-              </li>
               <li>
                 <input
                   id='is_rtl'