chore: upgrade the langchain community (#122)

* 移除魔改版 SupabaseVectorStore

官方已发版：https://github.com/langchain-ai/langchain/releases/tag/langchain-community%3D%3D0.2.1

Author: xingwanying

server/rag/retrieval.py

@@ -1,7 +1,7 @@
 import json
 from typing import Any
 from langchain_openai import OpenAIEmbeddings
-from rag.supabase_vectorstore import SupabaseVectorStore
+from langchain_community.vectorstores import SupabaseVectorStore
 from db.supabase.client import get_client
 from data_class import GitDocConfig, GitIssueConfig, S3Config
 from rag.github_file_loader import GithubFileLoader