Update QuitButtonEx.java

Author: janbodnar

lambda/QuitButtonEx.java

@@ -17,7 +17,7 @@ private void initUI() {
 
         var quitButton = new JButton("Quit");
 
-        quitButton.addActionListener(e -> System.exit(0));
+        quitButton.addActionListener(_ -> System.exit(0));
 
         createLayout(quitButton);