Use id instead of productid for <product>

Author: tomschr

src/docbuild/config/xml/data/portal-config-schema.rnc

@@ -557,9 +557,9 @@ ds.product =
     # not make sense to use xsd:id here because there can only ever be one
     # of these ID per productconfig file.
     (
+      ds.id.attr &
       ds.xmlbase.attr? &
       ds.path.attr? &
-      ds.productid.attr &  # TODO: use ds.id.attr?
       ds.schemaversion.attr? &
       ds.enabled.attr? &
       ds.site-section.attr? & # TODO: Do we still need this attribute?