Fix default redirects to owl-file instead of rdf

The default redirect for https://w3id.org/pmd/co and https://w3id.org/pmd/tto (and possibly others) point to https://materialdigital.github.io/tensile-test-ontology/ontology.rdf and similar. Since the switch to ODK we generate ttl and owl artefacts but not the latter. The .htaccess https://github.com/materialdigital/w3id/ needs to be adjustet, but I am lost there. Thanks for your help : )