Mute testIsFailureIndex (#106124)

Mute: https://github.com/elastic/elasticsearch/issues/106123

server/src/test/java/org/elasticsearch/cluster/metadata/DataStreamTests.java

@@ -1842,6 +1842,7 @@ public class DataStreamTests extends AbstractXContentSerializingTestCase<DataStr
         assertThat(failureStoreDataStream.getFailureStoreWriteIndex(), is(writeFailureIndex));
     }
 
+    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/106123")
     public void testIsFailureIndex() {
         boolean hidden = randomBoolean();
         boolean system = hidden && randomBoolean();