[OPENMP][DOCS] Update OpenMP status (NFC)

Summary: This is updating the OpenMP status table. Cray has volunteered for `defaultmap` and supporting `in_reduction` on the `target` construct, so the status on those entries from was changed from "unclaimed". Also, a new entry was added for supporting non-contiguous arrays sections on the `target update` directive.

Reviewers: ABataev, hfinkel, jdoerfert, kkwli0

Reviewed By: ABataev

Subscribers: guansong, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D69923