Fix parquet directories when config name is not a valid directory name
See https://github.com/huggingface/datasets-server/pull/985#issuecomment-1502148432 and comments above (https://github.com/huggingface/datasets-server/pull/985#discussion_r1160657830, https://github.com/huggingface/datasets-server/pull/985#discussion_r1160661131)
Fix parquet directories when config name is not a valid directory name: See https://github.com/huggingface/datasets-server/pull/985#issuecomment-1502148432 and comments above (https://github.com/huggingface/datasets-server/pull/985#discussion_r1160657830, https://github.com/huggingface/datasets-server/pull/985#discussion_r1160661131)