[AIRFLOW-3241] Remove Invalid template ext in GCS Sensors (#4076)
[AIRFLOW-3241] Remove Invalid template ext in GCS Sensors (#4076)

- Remove `template_ext = ('.sql',)`
- Fix Docstrings (Incorrect connection name and indentation)
owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow,owlabs/incubator-airflow