Add missing await

Author: saqadri

src/mcp/client/stdio/__init__.py

@@ -174,7 +174,7 @@ async def stdin_writer():
         finally:
             # Clean up process to prevent any dangling orphaned processes
             if sys.platform == "win32":
-                terminate_windows_process(process)
+                await terminate_windows_process(process)
             else:
                 process.terminate()