Fix flaky test that makes assumptions about other things on the heap

runtime/observatory/tests/service/object_graph_vm_test.dart

Index: runtime/observatory/tests/service/object_graph_vm_test.dart
diff --git a/runtime/observatory/tests/service/object_graph_vm_test.dart b/runtime/observatory/tests/service/object_graph_vm_test.dart
index 8b738cdb351662404eafadd4cb96ba4684d37f0b..65c8466ba962bacb0769d9dd67c321eada8be57a 100644
--- a/runtime/observatory/tests/service/object_graph_vm_test.dart
+++ b/runtime/observatory/tests/service/object_graph_vm_test.dart
@@ -32,7 +32,7 @@ void script() {
   lst = new List(2);
   lst[0] = lst; // Self-loop.
   // Larger than any other fixed-size list in a fresh heap.
-  lst[1] = new List(123456);
+  lst[1] = new List(1234569);
 }
 
 int fooId;