[subset] remove unnecessary check on name IDs

See: https://learn.microsoft.com/en-us/typography/opentype/spec/features_ae
The spec says they are expected to be in the font-specific name ID range (256–32767),
though that is not a requirement in this Feature Parameters specification.

src/hb-ot-layout-common.hh

@@ -646,8 +646,7 @@ struct FeatureParamsCharacterVariants
       return;
 
     unsigned last_name_id = (unsigned) firstParamUILabelNameID + (unsigned) numNamedParameters - 1;
-    if (last_name_id >= 256 && last_name_id <= 32767)
-      nameids_to_retain->add_range (firstParamUILabelNameID, last_name_id);
+    nameids_to_retain->add_range (firstParamUILabelNameID, last_name_id);
   }
 
   bool subset (hb_subset_context_t *c) const