refactor: Сделать POSITIVE_RATING константой

src/main/java/ru/yandex/practicum/filmorate/service/impl/UserServiceImpl.java

@@ -24,6 +24,7 @@
 @RequiredArgsConstructor
 @Slf4j
 public class UserServiceImpl implements UserService {
+    private static final int POSITIVE_RATING = 6;
 
     private final UserStorage userStorage;
     private final FilmStorage filmStorage;