⬆️ Upgrade eslint to v9

## Feature Request

Version under 9 are not supported anymore. 
Migrate to v9: https://eslint.org/docs/latest/use/migrate-to-9.0.0

When it is done, you can remove eslint from this list:
https://github.com/numerique-gouv/impress/blob/b898ca0ef9d177f2bd7b35044cd21c33e3ef29ae/renovate.json#L16