Mute MlMigrationIT#testConfigMigration (see #44621)

Author: Andrey Ershov

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

@@ -93,7 +93,8 @@ private void createTestIndex() throws IOException {
                 "}}}}");
         client().performRequest(createTestIndex);
     }
-    
+
+    @AwaitsFix(bugUrl = "https://github.com/elastic/elasticsearch/issues/44621")
     public void testConfigMigration() throws Exception {
         if (UPGRADED_FROM_VERSION.onOrAfter(Version.V_6_6_0)) {
             // We are testing migration of ml config defined in the clusterstate