修正しました

backend/src/main/java/com/example/todoapp/controller/ToBuysController.java

@@ -125,9 +125,6 @@ public class ToBuysController {
                 })
                 .collect(Collectors.toList());
 
-        // Map<String, Object> responseBody = new HashMap<>();
-        // responseBody.put("tobuy_array", responseList);
-
         return ResponseEntity.ok(responseList);
     }