Align __exit__ typing with repo convention (BlobPayloadStore)

Use `*args: object` for the `__exit__` parameters instead of leaving
them untyped. This matches the most recent context-manager class in
the repo (`durabletask/extensions/azure_blob_payloads/blob_payload_store.py`),
is more type-safe under Pylance/mypy, and avoids the parameter
shadowing of the builtin `type` that exists in
`TaskHubGrpcWorker.__exit__`. Behavior is unchanged.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Bernd Verst

durabletask/client.py

@@ -369,7 +369,7 @@ def close(self) -> None:
     def __enter__(self) -> "TaskHubGrpcClient":
         return self
 
-    def __exit__(self, exc_type, exc_val, exc_tb) -> None:
+    def __exit__(self, *args: object) -> None:
         self.close()
 
     def schedule_new_orchestration(self, orchestrator: task.Orchestrator[TInput, TOutput] | str, *,