feat - #67 일별챌린지 controller가 인터페이스 구현하도록 수정

src/main/java/sopt/org/HMH/domain/dailychallenge/controller/DailyChallengeController.java

@@ -19,7 +19,7 @@
 @RestController
 @RequiredArgsConstructor
 @RequestMapping("/api/v1/dailychallenge")
-public class DailyChallengeController {
+public class DailyChallengeController implements DailyChallengeApi {
 
     private final DailyChallengeService dailyChallengeService;