chore: apply ruff's pyupgrade linter rules to modernize Python code with targeted version (#2419)

api/core/index/base.py

@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from abc import ABC, abstractmethod
-from typing import Any, List
+from typing import Any
 
 from langchain.schema import BaseRetriever, Document
 
@@ -53,7 +53,7 @@ class BaseIndex(ABC):
     def search(
             self, query: str,
             **kwargs: Any
-    ) -> List[Document]:
+    ) -> list[Document]:
         raise NotImplementedError
 
     def delete(self) -> None: