Update the yamllint configuration to mostly match what M-C is currently using.
MozReview-Commit-ID: BeuXvpvAY53 --HG-- extra : rebase_source : f15458098c2ef78d25ce1c4b51a86d779a0075ca extra : amend_source : d03ad9d435c9dd35c6019edf4e431d50a7634045