[CHORE]: remove redundant-cast (#24807)

api/services/annotation_service.py

@@ -1,5 +1,5 @@
 import uuid
-from typing import cast
+from typing import Optional
 
 import pandas as pd
 from flask_login import current_user
@@ -40,7 +40,7 @@ class AppAnnotationService:
             if not message:
                 raise NotFound("Message Not Exists.")
 
-            annotation = message.annotation
+            annotation: Optional[MessageAnnotation] = message.annotation
             # save the message annotation
             if annotation:
                 annotation.content = args["answer"]
@@ -70,7 +70,7 @@ class AppAnnotationService:
                 app_id,
                 annotation_setting.collection_binding_id,
             )
-        return cast(MessageAnnotation, annotation)
+        return annotation
 
     @classmethod
     def enable_app_annotation(cls, args: dict, app_id: str) -> dict: