Use deserialize_unit instead of deserialize_any for unit variants of untagged and adjacently tagged enums

Author: Mingun

serde_derive/src/de.rs

@@ -1925,7 +1925,7 @@ fn deserialize_untagged_variant(
                 quote!((#default))
             });
             quote_expr! {
-                match _serde::Deserializer::deserialize_any(
+                match _serde::Deserializer::deserialize_unit(
                     #deserializer,
                     _serde::#private::de::UntaggedUnitVisitor::new(#type_name, #variant_name)
                 ) {