clean: Remove ctor_kind from VariantStruct.

It's always `None`.

src/librustdoc/clean/mod.rs

@@ -1960,7 +1960,6 @@ pub(crate) fn clean_variant_def<'tcx>(variant: &ty::VariantDef, cx: &mut DocCont
             variant.fields.iter().map(|field| clean_middle_field(field, cx)).collect(),
         ),
         None => VariantKind::Struct(VariantStruct {
-            ctor_kind: None,
             fields: variant.fields.iter().map(|field| clean_middle_field(field, cx)).collect(),
         }),
     };
@@ -1985,7 +1984,6 @@ fn clean_variant_data<'tcx>(
 
     let kind = match variant {
         hir::VariantData::Struct(..) => VariantKind::Struct(VariantStruct {
-            ctor_kind: None,
             fields: variant.fields().iter().map(|x| clean_field(x, cx)).collect(),
         }),
         hir::VariantData::Tuple(..) => {

src/librustdoc/clean/types.rs

@@ -2111,7 +2111,6 @@ impl Union {
 /// only as a variant in an enum.
 #[derive(Clone, Debug)]
 pub(crate) struct VariantStruct {
-    pub(crate) ctor_kind: Option<CtorKind>,
     pub(crate) fields: Vec<Item>,
 }
 

src/librustdoc/html/render/print_item.rs

@@ -1229,16 +1229,7 @@ fn item_enum(w: &mut Buffer, cx: &mut Context<'_>, it: &clean::Item, e: &clean::
                                 w.write_str(")");
                             }
                             clean::VariantKind::Struct(ref s) => {
-                                render_struct(
-                                    w,
-                                    v,
-                                    None,
-                                    s.ctor_kind,
-                                    &s.fields,
-                                    "    ",
-                                    false,
-                                    cx,
-                                );
+                                render_struct(w, v, None, None, &s.fields, "    ", false, cx);
                             }
                         },
                         _ => unreachable!(),