Add semicolon for example code style consistency (reactjs#575)

Author: bayprogrammer

content/docs/conditional-rendering.md

@@ -209,7 +209,7 @@ function WarningBanner(props) {
 class Page extends React.Component {
   constructor(props) {
     super(props);
-    this.state = {showWarning: true}
+    this.state = {showWarning: true};
     this.handleToggleClick = this.handleToggleClick.bind(this);
   }