ont: Adds missing prefix (in deprecated) [fix]

Author: hoijui

src/spec/okh_deprecated.ttl

@@ -8,6 +8,7 @@
 @prefix rdfs:     <http://www.w3.org/2000/01/rdf-schema#> .
 @prefix schema:   <http://schema.org/> .
 @prefix skos:     <http://www.w3.org/2004/02/skos/core#> .
+@prefix spdx:     <http://spdx.org/rdf/terms#> .
 @prefix vs:       <http://www.w3.org/2003/06/sw-vocab-status/ns#> .
 @prefix xsd:      <http://www.w3.org/2001/XMLSchema#> .