UMLTP23 — Empty sections shall be removed from the spec

The empty sections 8.7.1 Arbitration Specifications and section 8.7.1.1 Arbitration Facility are relicts from UTP 2.1. They should be removed from the editorial contents of the spec. This will cause a renumbering of current section 7.2 to 7.1 and current section 7.3 to 7.2. The renumbering affects all subsection of these two sections transitively.