Update kubernetes-on-aws-node-pool.md
Update kubernetes-on-aws-node-pool.md

Make a plain-text code-block to a yaml one
danielfm/kube-aws,HotelsDotCom/kube-aws,mumoshu/kube-aws,c-knowles/kube-aws,camilb/kube-aws,HotelsDotCom/kube-aws,everpeace/kube-aws,everpeace/kube-aws,iflix-letsplay/kube-aws,mumoshu/kube-aws,iflix-letsplay/kube-aws,c-knowles/kube-aws,danielfm/kube-aws,kubernetes-incubator/kube-aws,camilb/kube-aws,kubernetes-incubator/kube-aws