fix: minor updates and bug fixes

[DSuveges]

✨ Context

Upon QCing the 24.03 data release a few issues surfaced. This pr meant to address them.

🛠 What does this PR implement

• Update the configuration of the variant index step to point to the right credible set dataset.
• Renaming the credible set dataset generated by the GWAS Catalog pre-process step to make their content more obvious.
• Applying credible interval filter on the PICSed loci to ensure only the 99% credible sets remain.

🚦 Before submitting

• Do these changes cover one single feature (one change at a time)?
• Did you read the contributor guideline?
• Did you make sure to update the documentation with your changes?
• Did you make sure there is no commented out code in this PR?
• Did you follow conventional commits standards in PR title and commit messages?
• Did you make sure the branch is up-to-date with the dev branch?
• Did you write any new necessary tests?
• Did you make sure the changes pass local tests (make test)?
• Did you make sure the changes pass pre-commit rules (e.g poetry run pre-commit run --all-files)?

[d0choa]

I didn't go into detail to check every changed path, so I assume all changes are for good.

Nothing controversial and important fix for the PICS pipeline