♻️ refactor: 사용하지 않는 변수 삭제

Author: jiwon1217

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

@@ -72,8 +72,6 @@ public class RoomService {
 
     private final MessageSender messageSender;
 
-    private static final int CONTINUE_DELAY = 3;
-
     public RoomCreateResponse saveRoom(RoomCreateRequest request) {
 
         QuizMinData quizMinData = quizService.getQuizMinData();