[stable][cinder] Proposal to remove John Griffith from cinder-stable-maint

John Griffith has taken on other commitments and stepped down as a cinder-core recently, so it doesn't make sense for him to continue on the cinder-stable-maint list. I'd like to acknowledge his role as "The Father of Cinder", though, and express my thanks on behalf of the Cinder team for all his past work on the project. cheers, brian