chore: 불필요 클래스 레벨 트랜잭션 삭제

Author: dlsrks1021

backend/src/main/java/io/f1/backend/domain/stat/app/StatService.java

@@ -19,7 +19,6 @@
 import org.springframework.transaction.annotation.Transactional;
 
 @Service
-@Transactional
 @RequiredArgsConstructor
 public class StatService {