Fix obsolete rule in ast_enum_of_structs

    warning: 1st rule of macro `ast_enum_of_structs` is never used
      --> src/macros.rs:56:5
       |
    56 | /     (
    57 | |         $(#[$enum_attr:meta])*
    58 | |         $pub:ident $enum:ident $name:ident #$tag:ident $body:tt
    59 | |         $($remaining:tt)*
    60 | |     ) => {
       | |_____^
       |
       = note: `#[warn(unused_macro_rules)]` on by default

src/macros.rs

@@ -53,15 +53,6 @@ macro_rules! ast_enum {
 }
 
 macro_rules! ast_enum_of_structs {
-    (
-        $(#[$enum_attr:meta])*
-        $pub:ident $enum:ident $name:ident #$tag:ident $body:tt
-        $($remaining:tt)*
-    ) => {
-        ast_enum!($(#[$enum_attr])* $pub $enum $name #$tag $body);
-        ast_enum_of_structs_impl!($pub $enum $name $body $($remaining)*);
-    };
-
     (
         $(#[$enum_attr:meta])*
         $pub:ident $enum:ident $name:ident $body:tt