tests: add coverage for efl_parent_set with invalidated parent object

this hits a codepath which was otherwise never triggered by unit tests

src/tests/eo/suite/eo_test_general.c

@@ -667,6 +667,8 @@ EFL_START_TEST(efl_refs)
    fail_if(!efl_invalidated_get(obj2));
    fail_if(!efl_invalidated_get(obj3));
 
+   efl_parent_set(obj2, obj3);
+
    efl_unref(obj);
    efl_unref(obj2);
    efl_unref(obj3);