Add @FixForMultiProject in EnrichPolicyMaintenanceService (elastic#132676)

As a reminder that we need to ensure the enrich indices are cleaned up
for all projects.

Author: nielsbauman

x-pack/plugin/enrich/src/main/java/org/elasticsearch/xpack/enrich/EnrichPolicyMaintenanceService.java

@@ -24,6 +24,7 @@
 import org.elasticsearch.common.component.LifecycleListener;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
+import org.elasticsearch.core.FixForMultiProject;
 import org.elasticsearch.core.TimeValue;
 import org.elasticsearch.index.Index;
 import org.elasticsearch.threadpool.Scheduler;
@@ -145,6 +146,7 @@ void concludeMaintenance() {
         maintenanceLock.release();
     }
 
+    @FixForMultiProject // We need to ensure that the enrich indices are cleaned up for all projects
     void cleanUpEnrichIndices() {
         // Get cluster state first because for a new index to exist there then it has to have already been added to the inflight list
         // If the new index is in the cluster state but not in the inflight list, then that means that the index name was removed from the