fix(process): remove client reference after disconnection

Remove the client reference from the ProcessThon class after disconnection to prevent potential memory leaks and ensure proper cleanup of resources. This change ensures that the client object is dereferenced and garbage collected after the disconnection process is completed.

thon/process.py

@@ -173,6 +173,7 @@ class ProcessThon(Data):
             await self.client(UpdateStatusRequest(offline=True))
         with contextlib.suppress(Exception):
             await self.client.disconnect()  # type: ignore  # ty:ignore[unused-ignore-comment]
+        del self.__client
 
     async def __aenter__(self) -> Self | str:
         r = await self.check()