message: fix(cli): correct help text
  Followup to
  Fix the meaning and formatting of the help text for the modified `--reference` arg.
diff: @@ -107,9 +107,8 @@ pub struct NextcladeDatasetListArgs {
  pub name: Option<String>,
  /// Restrict list to datasets based on this reference sequence (given its accession ID). Equivalent to `--attribute='reference=<value>'`.
  - /// Special values:
  - /// - "all" show datasets with any reference sequences
  - /// - "default" show datasets with any reference sequences
  + ///
  + /// Special values: "all" - shows datasets with any reference sequences; "default" - show only datasets with default reference sequence (as defined by the author of a given dataset).
  #[clap(long, short = 'r')]
  #[clap(value_hint = ValueHint::Other)]
  #[clap(default_value = "all")]
  