message: feat(cli): use index_v2.json
  See the corresponding PR in data repo:
diff: @@ -89,7 +89,7 @@ pub struct DatasetsIndexJson {
  impl DatasetsIndexJson {
  #[inline]
  pub fn download(http: &mut HttpClient) -> Result<Self, Report> {
  - Self::from_str(&http.get(&"/index.json").wrap_err("When downloading dataset index")?)
  + Self::from_str(&http.get(&"/index_v2.json").wrap_err("When downloading dataset index")?)
  }
  }
  