Remove ARKINDEX_API_INTERNAL_URL
This was added for backwards compatibility with a variable used in Ponos workflows before it was renamed ARKINDEX_API_URL
in July 2019 (https://gitlab.com/arkindex/backend/commit/f4aa4f876555c09920a4608a9e34959e1c36c05e/), and has never been documented.
Edited by Erwan Rouchet