fix: PostSwipeEvent 내 에러 수정

Author: vectorch9

src/main/java/daybyquest/post/domain/PostSwipedEvent.java

@@ -4,7 +4,7 @@
 import lombok.Getter;
 
 @Getter
-public class PostSwipedEvent extends Event {
+public class PostSwipedEvent implements Event {
 
     private final Long userId;