Add sleep 0 for scheling cleanup tasks.

src/promptflow-core/promptflow/executor/_async_nodes_scheduler.py

@@ -132,6 +132,8 @@ async def _wait_and_complete_nodes(
             for task in tasks:
                 if not task.done():
                     task.cancel()
+            # Wait for the cancelled tasks to be scheduled to cleanup
+            await asyncio.sleep(0)
             err_msg = f"Line execution timeout after {line_timeout_sec} seconds."
             context.cancel_node_runs(err_msg)
             raise LineExecutionTimeoutError(context._line_number, line_timeout_sec)