Fix : swagger 설명 안달린 것 추가

src/main/java/Chaeda_spring/domain/textbook/controller/TextbookController.java

@@ -33,6 +33,7 @@ public ResponseEntity<TextbookUrlResponse> createPresignedUrl(
     }
 
     @PostMapping("/uploadCompleted")
+    @Operation(summary = "교재 PDF S3 업로드 완료 요청")
     public ResponseEntity<Void> uploadCompleted(@RequestBody UploadTextbookFileRequest request) {
         textbookService.saveTextBook(request);
         return ResponseEntity.ok().body(null);