Mute ML upgrade test (#30458)

It fails fairly frequently. Some ML expert will look soon.

Author: alpar-t

x-pack/qa/rolling-upgrade/src/test/java/org/elasticsearch/upgrades/UpgradeClusterClientYamlTestSuiteIT.java

@@ -8,6 +8,7 @@
 import com.carrotsearch.randomizedtesting.annotations.ParametersFactory;
 import com.carrotsearch.randomizedtesting.annotations.TimeoutSuite;
 
+import org.apache.lucene.util.LuceneTestCase;
 import org.apache.lucene.util.TimeUnits;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
@@ -29,6 +30,7 @@
 import static org.hamcrest.Matchers.is;
 
 @TimeoutSuite(millis = 5 * TimeUnits.MINUTE) // to account for slow as hell VMs
+@LuceneTestCase.AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/30456")
 public class UpgradeClusterClientYamlTestSuiteIT extends ESClientYamlSuiteTestCase {
 
     /**