refactor: 优化用户可见错误提示

src/main/java/com/guo/learningprogresstracker/dto/request/EndedStudySessionRequest.java

@@ -8,6 +8,6 @@ import lombok.Data;
  */
 @Data
 public class EndedStudySessionRequest {
-    @NotBlank(message = "啊？搞无字天书是吧？报告内容不可为空")
+    @NotBlank(message = "请填写学习报告内容")
     private String content;
 }