[AIRFLOW-4397] add integrations docs manually for gcs sensors (#5204)
[AIRFLOW-4397] add integrations docs manually for gcs sensors (#5204)


(cherry picked from commit 7eb7abe18513008bf7dc00b61a9ae05062ea5bb2)

owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow