[AIRFLOW-XXX] Update kubernetes.rst docs (#3875)
[AIRFLOW-XXX] Update kubernetes.rst docs (#3875)

Update kubernetes.rst with correct KubernetesPodOperator inputs
for the volumes.
owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow