Update cheatsheet.md

Add syntax to remove labels

content/en/docs/reference/kubectl/cheatsheet.md

@@ -266,6 +266,7 @@ kubectl expose rc nginx --port=80 --target-port=8000
 kubectl get pod mypod -o yaml | sed 's/\(image: myimage\):.*$/\1:v4/' | kubectl replace -f -
 
 kubectl label pods my-pod new-label=awesome                      # Add a Label
+kubectl label pods my-pod new-label-                             # Remove a label
 kubectl annotate pods my-pod icon-url=http://goo.gl/XXBTWq       # Add an annotation
 kubectl autoscale deployment foo --min=2 --max=10                # Auto scale a deployment "foo"
 ```