rdflib_jsonld breaks install, replace with RDFLib 6.0 integrated version

[Panaetius]

A big change in RDFlib 6.0 was integrating rdflib_jsonld into RDFlib itself: RDFLib/rdflib#1354

Due to this, the rdflib_jsonld project has been archived and is not maintained anymore: https://github.com/RDFLib/rdflib-jsonld#archived

Since rdflib_jsonld cannot be installed anymore with the newest version of setuptools, since it has use_2to3 set to true, see pypa/setuptools#2769, this makes OWL-RL uninstallable with JSON-LD with the newest version of setuptools.

I noticed this when trying to work on a PR for pySHACL to fix the same issue: RDFLib/pySHACL#93