fix: updates typing for python 3.8

Author: chalmerlowe

packages/google-cloud-storage/google/cloud/storage/asyncio/async_appendable_object_writer.py

@@ -15,7 +15,7 @@
 fromioimportBufferedReader
 importio
 importlogging
-fromtypingimportList, Optional, Tuple, Union
+fromtypingimportDict, List, Optional, Tuple, Union
 
 fromgoogle.api_coreimportexceptions
 fromgoogle.api_core.retry_asyncimportAsyncRetry
@@ -367,7 +367,7 @@ async def append(
 
 defsend_and_recv_generator(
 requests: List[BidiWriteObjectRequest],
-state: dict[str, _WriteState],
+state: Dict[str, _WriteState],
 metadata: Optional[List[Tuple[str, str]]] =None,
  ):
 asyncdefgenerator():