Refactor: remove useless initialize logic in list_doc (#8523)

### What problem does this PR solve?

Remove useless logic in a loop for list_doc

### Type of change

- [x] Refactoring
- [x] Performance Improvement

api/apps/sdk/doc.py

@@ -519,20 +519,20 @@ def list_docs(dataset_id, tenant_id):
 
     # rename key's name
     renamed_doc_list = []
+    key_mapping = {
+        "chunk_num": "chunk_count",
+        "kb_id": "dataset_id",
+        "token_num": "token_count",
+        "parser_id": "chunk_method",
+    }
+    run_mapping = {
+          "0": "UNSTART",
+          "1": "RUNNING",
+          "2": "CANCEL",
+          "3": "DONE",
+          "4": "FAIL",
+    }
     for doc in docs:
-        key_mapping = {
-            "chunk_num": "chunk_count",
-            "kb_id": "dataset_id",
-            "token_num": "token_count",
-            "parser_id": "chunk_method",
-        }
-        run_mapping = {
-            "0": "UNSTART",
-            "1": "RUNNING",
-            "2": "CANCEL",
-            "3": "DONE",
-            "4": "FAIL",
-        }
         renamed_doc = {}
         for key, value in doc.items():
             if key == "run":