Download parquet in split-duckdb-index
Fixes https://github.com/huggingface/datasets-server/issues/1686
Using hf_download instead of loading parquet files to duckdb directly.

Download parquet in split-duckdb-index: Fixes https://github.com/huggingface/datasets-server/issues/1686
Using hf_download instead of loading parquet files to duckdb directly.
