Fixed warning: SAWarning: Coercing Subquery object into a select() fo…

…r use in IN()

backend/oasst_backend/prompt_repository.py

@@ -397,7 +397,7 @@ def fetch_random_thread(self, require_role: str = None) -> list[Post]:
             distinct_threads = distinct_threads.filter(Post.role == require_role)
         distinct_threads = distinct_threads.subquery()
 
-        random_thread = self.db.query(distinct_threads).order_by(func.random()).limit(1).subquery()
+        random_thread = self.db.query(distinct_threads).order_by(func.random()).limit(1)
         thread_posts = self.db.query(Post).filter(Post.thread_id.in_(random_thread)).all()
         return thread_posts
 
@@ -443,7 +443,7 @@ def fetch_multiple_random_replies(self, max_size: int = 5, post_role: str = None
         if post_role:
             parent = parent.filter(Post.role == post_role)
 
-        parent = parent.order_by(func.random()).limit(1).subquery()
+        parent = parent.order_by(func.random()).limit(1)
         replies = self.db.query(Post).filter(Post.parent_id.in_(parent)).order_by(func.random()).limit(max_size).all()
         if not replies:
             raise OasstError("No replies found", OasstErrorCode.NO_REPLIES_FOUND)