Update `python-build-standalone` workflow (#5390)
## Summary
After #5337, `fetch-download-metadata.py` fetches not just from
`python-build-standalone`, so updates the workflow to
`sync-python-releases.yml`.
Also includes `crates/uv-python/download-metadata.json` in `add-paths`.
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Co-authored-by: Zanie Blue <contact@zanie.dev>
