not for upstream: added disposing frames in order to provide the test with the chance on the second run

(cherry picked from commit 8170635)
(cherry picked from commit 7fc924f065)

test/jdk/java/awt/Window/Grab/GrabTest.java

@@ -123,6 +123,10 @@ public class GrabTest {
         Util.waitForIdle(robot);
 
         test();
+
+        frame.dispose();
+        f1.dispose();
+        f.dispose();
     }
 
     public static void test() {