Revert "Use `dash==2.8.1` for now for daily CI"
Reverts huggingface/transformers#22227

New version [dash 2.9.1](https://github.com/plotly/dash/releases/tag/v2.9.1) works with our CI. Tested and it works.
We no longer need the change in #22227

The docs for this PR live [here](https://moon-ci-docs.huggingface.co/docs/transformers/pr_22233). All of your documentation changes will be reflected on that endpoint.