Adjust some comments on THIR PatKind::Variant and PatKind::Leaf

`PatKind::Variant` is always used for enum variants, even for enums that only
have one variant.

Author: Zalathar

compiler/rustc_middle/src/thir.rs

@@ -788,17 +788,15 @@ pub enum PatKind<'tcx> {
         is_shorthand: bool,
     },
 
-    /// `Foo(...)` or `Foo{...}` or `Foo`, where `Foo` is a variant name from an ADT with
-    /// multiple variants.
+    /// `Foo(..)` or `Foo { .. }` or `Foo`, where `Foo` is an enum variant.
     Variant {
         adt_def: AdtDef<'tcx>,
         args: GenericArgsRef<'tcx>,
         variant_index: VariantIdx,
         subpatterns: Vec<FieldPat<'tcx>>,
     },
 
-    /// `(...)`, `Foo(...)`, `Foo{...}`, or `Foo`, where `Foo` is a variant name from an ADT with
-    /// a single variant.
+    /// `(..)`, `Foo(..)`, `Foo { .. }`, or `Foo`, where `Foo` is a struct.
     Leaf {
         subpatterns: Vec<FieldPat<'tcx>>,
     },