Remove event from arrow function example (#1542)

content/docs/handling-events.md

@@ -130,7 +130,7 @@ class LoggingButton extends React.Component {
   render() {
     // This syntax ensures `this` is bound within handleClick
     return (
-      <button onClick={(e) => this.handleClick(e)}>
+      <button onClick={() => this.handleClick()}>
         Click me
       </button>
     );