Add license header to EqlStatsIT.java (#59537)

x-pack/plugin/eql/qa/rest/src/test/java/org/elasticsearch/xpack/eql/EqlStatsIT.java

@@ -1,3 +1,9 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License;
+ * you may not use this file except in compliance with the Elastic License.
+ */
+
 package org.elasticsearch.xpack.eql;
 
 import org.elasticsearch.test.eql.stats.RestEqlUsageTestCase;