[hotfix] 세트 삭제 안됨 이슈 해결

Author: sejoon00

src/main/java/com/moplus/moplus_server/domain/problemset/service/ProblemSetDeleteService.java

@@ -15,6 +15,7 @@ public class ProblemSetDeleteService {
     @Transactional
     public void deleteProblemSet(Long problemSetId) {
         ProblemSet problemSet = problemSetRepository.findByIdElseThrow(problemSetId);
+        problemSetRepository.delete(problemSet);
     }
 
 }