suppres warning

app/src/main/java/chess/view/simplerender/Window.java

@@ -60,6 +60,7 @@ public class Window extends JFrame implements GameListener, CommandSender {
 		return ((x + y) % 2 == 1) ? Color.DARK_GRAY : Color.LIGHT_GRAY;
 	}
 
+	@SuppressWarnings("unused")
 	private void buildButtons(JPanel bottom) {
 		castlingButton.addActionListener((event) -> {
 			sendCastling();