message: Fix trait object in doctest
diff: @@ -128,7 +128,7 @@ impl TopDocs {
  /// ///
  /// /// `field` is required to be a FAST field.
  /// fn docs_sorted_by_rating(searcher: &Searcher,
  - /// query: &Query,
  + /// query: &dyn Query,
  /// sort_by_field: Field)
  /// -> Result<Vec<(u64, DocAddress)>> {
  ///
  