fix: updateThesis 서비스에서 저장이 되지 않는 오류 수정

Author: JangYeongHu

aics-domain/src/main/java/kgu/developers/domain/graduationUser/application/command/GraduationUserCommandService.java

@@ -56,5 +56,6 @@ public void updateThesis(GraduationUser graduationUser, Long thesisId, ThesisTyp
             case MID_THESIS -> graduationUser.updateMidThesisId(thesisId);
             case FINAL_THESIS -> graduationUser.updateFinalThesisId(thesisId);
         }
+        graduationUserRepository.save(graduationUser);
     }
 }