Improve example for EndpointSlice label

Use the most common value for this label
(endpointslice.kubernetes.io/managed-by) as the example value.

Author: Tim Bannister

content/en/docs/reference/labels-annotations-taints/_index.md

@@ -1117,7 +1117,7 @@ duration (defaults to one year).
 
 Type: Label
 
-Example: `endpointslice.kubernetes.io/managed-by: "controller"`
+Example: `endpointslice.kubernetes.io/managed-by: endpointslice-controller.k8s.io`
 
 Used on: EndpointSlices