Context for WBbt_*

I was looking at this GO-CAM model and it uses an URI http://purl.obolibrary.org/obo/WBbt_0003679 without CURIE in https://github.com/prefixcommons/biocontext/blob/master/registry/go_context.jsonld. 

However, it seems the [db-xrefs.yaml](https://github.com/geneontology/go-site/blob/master/metadata/db-xrefs.yaml) has this CURIE <-> IRI, so @cmungall could we update the go_context.jsonld ?

