[editor] GitHub roles

Hi all, I've had a quick cleanup of the roles on GitHub. Jonas and Sam have both retired from Editorship, so I've removed them. Additionally, Flow, JC and Martin aren't active in merging people's PRs so on 'least privilege' I've removed them too (Peter isn't active either, but as he's org admin, removing him would have little efect, AFAIK). Obviously, any of this is trivially reversed if someone *is* doing work that needs write to the repo - please shout if so and I shall place my tail between my legs and fix it. /K