concurrent merge is another mvcc test we don't care about in multithreaded mode

h2/src/test/org/h2/test/mvcc/TestMvccMultiThreaded.java

@@ -31,9 +31,9 @@ public class TestMvccMultiThreaded extends TestBase {
     @Override
     public void test() throws Exception {
         testMergeWithUniqueKeyViolation();
-        testConcurrentMerge();
         // not supported currently
         if (!config.multiThreaded) {
+            testConcurrentMerge();
             testConcurrentUpdate();
         }
     }