🔧 chore: 사용하지 않는 상수 삭제

Author: silver-eunjoo

backend/src/main/java/io/f1/backend/domain/game/app/GameService.java

@@ -32,7 +32,6 @@
 public class GameService {
 
     private static final int START_DELAY = 5;
-    private static final int CONTINUE_DELAY = 3;
 
     private final MessageSender messageSender;
     private final TimerService timerService;