apiVersion: v1
data:
  X-Different-Name: "true"
  X-Request-Start: t=${msec}
  X-Using-Nginx-Controller: "true"
kind: ConfigMap
metadata:
  name: proxy-headers
  namespace: kube-system

apiVersion: v1
data:
  X-Different-Name: "true"
  X-Request-Start: t=${msec}
  X-Using-Nginx-Controller: "true"
kind: ConfigMap
metadata:
  name: custom-headers
  namespace: kube-system

Fix config name in the example.
Fix config name in the example. 

Replace `proxy-headers` with `custom-headers` to match [nginx-load-balancer-conf.yaml](https://github.com/kubernetes/ingress/blob/master/examples/customization/custom-headers/nginx/nginx-load-balancer-conf.yaml#L3)