Remove unused ILMHistoryStore in IndexLifeycleService (#69503)

this commit removes unused instance variable for
the ILMHIstoryStore in IndexLifecycleService. Although
it is passed in as an argument to the constructor, it
is only used by the IndexLifecycleRunner.

Author: talevy

x-pack/plugin/ilm/src/main/java/org/elasticsearch/xpack/ilm/IndexLifecycleService.java

@@ -63,7 +63,6 @@ public class IndexLifecycleService
     private final Clock clock;
     private final PolicyStepsRegistry policyRegistry;
     private final IndexLifecycleRunner lifecycleRunner;
-    private final ILMHistoryStore ilmHistoryStore;
     private final Settings settings;
     private ClusterService clusterService;
     private LongSupplier nowSupplier;
@@ -78,7 +77,6 @@ public IndexLifecycleService(Settings settings, Client client, ClusterService cl
         this.clock = clock;
         this.nowSupplier = nowSupplier;
         this.scheduledJob = null;
-        this.ilmHistoryStore = ilmHistoryStore;
         this.policyRegistry = new PolicyStepsRegistry(xContentRegistry, client);
         this.lifecycleRunner = new IndexLifecycleRunner(policyRegistry, ilmHistoryStore, clusterService, threadPool, nowSupplier);
         this.pollInterval = LifecycleSettings.LIFECYCLE_POLL_INTERVAL_SETTING.get(settings);