Merge paradox/scala/cluster-metrics.md and java/cluster-metrics.md (#23098)

* Identical contents in scala/cluster-metrics.md and java/cluster-metrics.md for easier review

* Replace java/cluster-metrics.md with a symlink to scala/cluster-metrics.md

* Fix typo

akka-docs/src/test/java/jdocs/cluster/FactorialFrontend.java

@@ -83,6 +83,7 @@ abstract class FactorialFrontend2 extends AbstractActor {
       HeapMetricsSelector.getInstance(), Collections.<String> emptyList()),
         new ClusterRouterGroupSettings(totalInstances, routeesPaths,
           allowLocalRoutees, useRole)).props(), "factorialBackendRouter2");
+
   //#router-lookup-in-code
 }