[dxwg] new commits pushed by agbeltran

The following commits were just pushed by agbeltran to https://github.com/w3c/dxwg:

* Remove sub-property axiom for consistency with document
- see https://github.com/w3c/dxwg/issues/175
  by Simon Cox
https://github.com/w3c/dxwg/commit/cc4ccbbed97ef7cf083ec50a554c67efb0c3f023

* Merge pull request #250 from w3c/dcat-rdf-bugs

dcat:keyword - Remove sub-property axiom for consistency with document
  by Alejandra Gonzalez-Beltran
https://github.com/w3c/dxwg/commit/20ba15a4c61132eb0819350fc77f4b44738d54d3