Use deserialize_map when deserialize internally tagged enums

Deserializer methods are only hints which deserializer is not obliged to follow.

Both
- TaggedContentVisitor
- InternallyTaggedUnitVisitor

accepts only visit_map and visit_seq and that is what derived implementation of
Deserialize does for structs. Therefore it is fine to call deserialize_map here,
as that already did in derived deserialize implementation. Because those structs
officially not public, it is used only by derive macro

serde_derive/src/de.rs

@@ -1055,7 +1055,7 @@ fn deserialize_struct(
  _serde::de::VariantAccess::struct_variant(__variant, FIELDS, #visitor_expr)
  },
  StructForm::InternallyTagged(_, deserializer) => quote! {
- _serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
+ _serde::Deserializer::deserialize_map(#deserializer, #visitor_expr)
  },
  StructForm::Untagged(_, deserializer) => quote! {
  _serde::Deserializer::deserialize_any(#deserializer, #visitor_expr)
@@ -1436,7 +1436,7 @@ fn deserialize_internally_tagged_enum(
  }
  }
 
- _serde::Deserializer::deserialize_any(
+ _serde::Deserializer::deserialize_map(
  __deserializer,
  _serde::__private::de::TaggedContentVisitor::<__Seed>::new(#tag, #expecting)
  )
@@ -1892,7 +1892,7 @@ fn deserialize_internally_tagged_variant(
  quote!((#default))
  });
  quote_block! {
- _serde::Deserializer::deserialize_any(#deserializer, _serde::__private::de::InternallyTaggedUnitVisitor::new(#type_name, #variant_name))?;
+ _serde::Deserializer::deserialize_map(#deserializer, _serde::__private::de::InternallyTaggedUnitVisitor::new(#type_name, #variant_name))?;
  _serde::__private::Ok(#this_value::#variant_ident #default)
  }
  }