Update Superset demos to use Open Street Maps

[NickLarsenNZ]

Superset now default to OSM.

We need to update the demos which select Mapbox styles.

At least these two:

• https://docs.stackable.tech/home/stable/demos/nifi-kafka-druid-water-level-data/#_view_the_dashboard
• https://docs.stackable.tech/home/stable/demos/nifi-kafka-druid-earthquake-data/#_view_the_dashboard

[NickLarsenNZ]

Already fixed by #385