fix: close write object stream always (#1661)

fix: close write object stream always. otherwise Task will remain for long time until GC kills it and it'll
throw this `"Task was destroyed but it is pending!"`

Author: chandra-siri

google/cloud/storage/_experimental/asyncio/async_appendable_object_writer.py

@@ -267,7 +267,8 @@ async def close(self, finalize_on_close=False) -> Union[int, _storage_v2.Object]
 awaitself.finalize()
 else:
 awaitself.flush()
-awaitself.write_obj_stream.close()
+
+awaitself.write_obj_stream.close()
 
 self._is_stream_open=False
 self.offset=None

tests/unit/asyncio/test_async_appendable_object_writer.py

@@ -313,7 +313,7 @@ async def test_finalize_on_close(mock_write_object_stream, mock_client):
 result=awaitwriter.close(finalize_on_close=True)
 
 # Assert
-mock_stream.close.assert_not_awaited() # Based on new implementation
+mock_stream.close.assert_awaited_once()
 assertnotwriter._is_stream_open
 assertwriter.offsetisNone
 assertwriter.object_resource==mock_resource