fix: 댓글 삭제 시 댓글 수가 반영되지 않는 버그 수정

* fix: 댓글 삭제 시 개수가 줄어들지 않는 버그 수정

* refactor: 코드 간결하게 수정

src/main/java/com/ssafy/ssafsound/domain/post/dto/GetPostElement.java

@@ -38,13 +38,18 @@ public GetPostElement(Post post) {
         this.title = post.getTitle();
         this.content = post.getContent();
         this.likeCount = post.getLikes().size();
-        this.commentCount = post.getComments().size();
+        this.commentCount = getCommentSize(post);
         this.createdAt = post.getCreatedAt();
         this.nickname = anonymity ? "익명" : post.getMember().getNickname();
         this.anonymity = anonymity;
         this.thumbnail = findThumbnailUrl(post);
     }
 
+    private int getCommentSize(Post post) {
+        return (int) post.getComments().stream()
+                .filter(comment -> !comment.getDeletedComment()).count();
+    }
+
     private String findThumbnailUrl(Post post) {
         List<PostImage> images = post.getImages();
         if (images.size() >= 1)