Change stackforge acl tags example to -ptl from -core

Project acls in the refs/tags/* stanza should specific the ptl
of a program/project as opposed to all the core reviewers. This
patch changes the stackforge acl example to reflect this.

Also this patch changes WIP to Workflow in the explanation below
which is more consistent with Gerrit 2.8 functionality.

Change-Id: If7df749b54d5ace8904ea1def900618a196aa265