use support.rmtree instead of shutil (closes #19614)

Patch by Sean Rodman.
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 5913044..cb6f84e 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -102,7 +102,7 @@
                 self.assertTrue(os.path.isdir(path))
             self.assertFalse(os.path.isdir(path))
         finally:
-            shutil.rmtree(parent_dir)
+            support.rmtree(parent_dir)
 
     def test_temp_dir__path_none(self):
         """Test passing no path."""