typo fix nw-networkpolicy-about.adoc

While copy and pasting the example policy from the documentation, the policy creation was failed with the below error,

`Error from server (BadRequest): error when creating "host.yaml": NetworkPolicy in version "v1" cannot be handled as a NetworkPolicy: json: cannot unmarshal string into Go struct field LabelSelector.spec.ingress.from.namespaceSelector.matchLabels of type map[string]string`

There was a indentation error in spec.ingress.from.namespaceSelector.matchLabels 

policy-group.network.openshift.io/ingress:""
policy-group.network.openshift.io/host-network:""

Author: anandrece

modules/nw-networkpolicy-about.adoc

@@ -144,7 +144,7 @@ spec:
   - from:
     - namespaceSelector:
         matchLabels:
-          policy-group.network.openshift.io/ingress:""<1>
+          policy-group.network.openshift.io/ingress: ""<1>
   podSelector: {}
   policyTypes:
   - Ingress
@@ -168,7 +168,7 @@ spec:
   - from:
     - namespaceSelector:
         matchLabels:
-          policy-group.network.openshift.io/host-network:""
+          policy-group.network.openshift.io/host-network: ""
   podSelector: {}
   policyTypes:
   - Ingress