`dag` parameter not required because the operator is in the DAG context already

[roger-yu-ds]

https://github.com/GoogleCloudPlatform/mlops-on-gcp/blob/2ef4c5bce2fbd356b3018b1ed981f151a7520003/continuous_training/composer/labs/chicago_taxi_dag.py#LL207C1-L207C1