Fix minor typo in federation example (#685)

Author: Tim Middleton

examples/100_federation/src/main/yaml/secondary-cluster.yaml

@@ -18,7 +18,7 @@ spec:
       - "-Dprimary.cluster=primary-cluster"
       - "-Dprimary.cluster.port=40000"
       - "-Dprimary.cluster.host=primary-cluster-federation"
-      - "-Dprimary.cluster=secondary-cluster"
+      - "-Dsecondary.cluster=secondary-cluster"
       - "-Dsecondary.cluster.port=40000"
       - "-Dsecondary.cluster.host=secondary-cluster-federation"
   secretVolumes: