fix: import Annotated from typing_extensions for Python 3.8 compatibility

docs_src/query_params_str_validations/tutorial006d_an_py310.py

@@ -1,4 +1,5 @@
-from typing import Annotated, Optional, Union
+from typing import Optional, Union
+from typing_extensions import Annotated
 
 from fastapi import FastAPI, Query
 from pydantic import BeforeValidator