downgrade gradio to avoid error
already reverted in the space https://huggingface.co/spaces/datasets-maintainers/datasets-server-admin-ui

see https://github.com/huggingface/datasets-server/issues/2228
downgrade gradio to avoid error: already reverted in the space https://huggingface.co/spaces/datasets-maintainers/datasets-server-admin-ui

see https://github.com/huggingface/datasets-server/issues/2228