Ensure we use our ETL regions everywhere in grapher

[pabloarosado]

Currently, our page on world region definitions uses very old datasets that were manually uploaded. They are not totally consistent with our regions dataset. For example, OWID regions include "French Southern Territories" (visible in the map) as well as other regions that belong to Antarctica.

It would be better to use the indicator from our grapher/regions/2023-01-01/regions dataset. The same applies to WHO and other institution regions (which would need to be added to the garden/regions step).

Similarly, scatter plots use "Continents" from that old manually uploaded dataset, and it would be better to use our regions step. In this case, however, note that:

• Grapher needs to hide the origin of this dataset. When using the new indicator, it seems that the origin is not hidden (probably because the variable id of the old continents indicator is hardcoded.
• In this special case, it's not clear to me if here we want to use the grapher indicator, or the external one.