Set tap-fastly default variant to splitio
The tap-fastly default variant is still https://gitlab.com/meltano/tap-fastly which hasnt been updated in 2 years. We should replace it with the splitio variant which seems to be based off the meltano variant but has more recent maitenance https://github.com/splitio/tap-fastly.
Then we're free to archive the meltano variant repo.