assign-pod-node: pod affinity can't apply to all namespaces (#9876)

See kubernetes/kubernetes#67475

content/en/docs/concepts/configuration/assign-pod-node.md

@@ -167,7 +167,7 @@ Inter-pod affinity and anti-affinity were introduced in Kubernetes 1.4.
 Inter-pod affinity and anti-affinity allow you to constrain which nodes your pod is eligible to be scheduled *based on
 labels on pods that are already running on the node* rather than based on labels on nodes. The rules are of the form "this pod should (or, in the case of
 anti-affinity, should not) run in an X if that X is already running one or more pods that meet rule Y". Y is expressed
-as a LabelSelector with an associated list of namespaces (or "all" namespaces); unlike nodes, because pods are namespaced
+as a LabelSelector with an associated list of namespaces; unlike nodes, because pods are namespaced
 (and therefore the labels on pods are implicitly namespaced),
 a label selector over pod labels must specify which namespaces the selector should apply to. Conceptually X is a topology domain
 like node, rack, cloud provider zone, cloud provider region, etc. You express it using a `topologyKey` which is the
@@ -224,8 +224,7 @@ empty `topologyKey` is not allowed.
 
 In addition to `labelSelector` and `topologyKey`, you can optionally specify a list `namespaces`
 of namespaces which the `labelSelector` should match against (this goes at the same level of the definition as `labelSelector` and `topologyKey`).
-If omitted, it defaults to the namespace of the pod where the affinity/anti-affinity definition appears.
-If defined but empty, it means "all namespaces".
+If omitted or empty, it defaults to the namespace of the pod where the affinity/anti-affinity definition appears.
 
 All `matchExpressions` associated with `requiredDuringSchedulingIgnoredDuringExecution` affinity and anti-affinity
 must be satisfied for the pod to be scheduled onto a node.