feat: board 전체조회 결과가 없는 경우 수정

backend/src/main/java/com/edufocus/edufocus/board/controller/BoardController.java

@@ -37,9 +37,6 @@ public class BoardController {
     ){
         List<ResponseBoardSummaryDto> boardSummaries = boardService.findBoards(pageNo, category, lectureId);
 
-        if(boardSummaries.isEmpty())
-            return new ResponseEntity<>(boardSummaries, HttpStatus.NO_CONTENT);
-
         return new ResponseEntity<>(boardSummaries, HttpStatus.OK);
     }