Perf: set timeout of some steps in KG. (#8873)

### What problem does this PR solve?

### Type of change


- [x] Performance Improvement

api/settings.py

@@ -26,7 +26,6 @@ import rag.utils.opensearch_conn
 from api.constants import RAG_FLOW_SERVICE_NAME
 from api.utils import decrypt_database_config, get_base_config
 from api.utils.file_utils import get_project_base_directory
-from graphrag import search as kg_search
 from rag.nlp import search
 
 LIGHTEN = int(os.environ.get("LIGHTEN", "0"))
@@ -169,6 +168,7 @@ def init_settings():
         raise Exception(f"Not supported doc engine: {DOC_ENGINE}")
 
     retrievaler = search.Dealer(docStoreConn)
+    from graphrag import search as kg_search
     kg_retrievaler = kg_search.KGSearch(docStoreConn)
 
     if int(os.environ.get("SANDBOX_ENABLED", "0")):