message: doc(ast_node): Remove an unnecessary comment
diff: @@ -156,9 +156,6 @@ impl VisitMut for AddAttr {
  /// `#[derive(Spanned, Fold, Clone, Debug, PartialEq)]` for a struct and
  /// `#[derive(Spanned, Fold, Clone, Debug, PartialEq, FromVariant)]` for an
  /// enum.
  -///
  -///
  -/// TODO: Delete works related to serde to `#[ast_serde]`.
  #[proc_macro_attribute]
  pub fn ast_node(
  args: proc_macro::TokenStream,
  