remove (event) from onClick event

README.md

@@ -70,7 +70,7 @@ class App extends Component {
   render() {
     return (
       <div className="App">
-        <button onClick={(event) => this.handleOnClick()}>
+        <button onClick={() => this.handleOnClick()}>
           Click
         </button>
         <p>{this.props.items.length}</p>