Skip serialization of remapped types.

JSON only supports string keys in maps and the remapped types isn't needed in
the `resolve` command output.

Author: peterhuene

crates/wac-parser/src/resolution/types.rs

@@ -394,7 +394,7 @@ pub struct Interface {
     ///
     /// Encoding uses this map to populate the encoded type index map for the
     /// original types.
-    #[serde(skip_serializing_if = "IndexMap::is_empty")]
+    #[serde(skip)]
     pub remapped_types: IndexMap<Type, IndexSet<Type>>,
     /// A map from used interface to set of used type export indexes.
     #[serde(serialize_with = "serialize_id_key_map")]