fixed matrixk2 test

src/test/java/UnifyTest.java

@@ -2099,7 +2099,7 @@ public class UnifyTest {
         TypeUnify unifyAlgo = new TypeUnify();
         ConstraintSet< Pair> cons = new ConstraintSet<>();
         UnifyResultModelParallel urm = new UnifyResultModelParallel(cons, finiteClosure);
-        UnifyTaskModelParallel tasks = new UnifyTaskModelParallel();
+        UnifyTaskModel tasks = new UnifyTaskModel();
         Set<Set<UnifyPair>> solution = unifyAlgo.unify(undConstraints, oderConstraints, finiteClosure, new NullWriter(), false, urm, tasks);
         System.out.println(solution.size());
     }