refactor: reorder tasks in genetics_etl

[project-defiant]

Context

• Clean up and removal of the code that synched gwas catalog manifest files (no longer required).
• Reorder the variant index steps so more clear.
• Removal of anchors in the config

This is a temporary solution for attempting to rerun just some steps from the genetics_etl configuration, althouth still required commenting out the code, now it is only a single block.