Remove mdemirhan from OWNERS#6161

Merged

knative-prow-robot merged 1 commit intoknative:masterfrom

mattmoor:scrub-owners

Dec 10, 2019

Commits on Dec 5, 2019

Per [responsibilities and privileges](https://github.com/knative/community/blob/master/ROLES.md#responsibilities-and-privileges-1) for approvers:
mattmoor
committed