Remove duplicate properties.
Remove duplicate properties.

See https://github.com/hbz/lobid-rdf-to-json/pull/45#commitcomment-19126572 and https://github.com/hbz/lobid-rdf-to-json/pull/45#commitcomment-19129021.

jschnasse/regal-api,edoweb/regal-api,jschnasse/regal-api,jschnasse/regal-api,edoweb/regal-api,hbz/lobid-rdf-to-json,edoweb/regal-api,edoweb/regal-api,jschnasse/regal-api