bpo-43916: Use test.support.check_disallow_instantiation() in test_tcl (GH-26412)

diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index cd3aacf6..e7a60db 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -738,9 +738,9 @@ def check(value):
 
     @support.cpython_only
     def test_new_tcl_obj(self):
-        self.assertRaises(TypeError, _tkinter.Tcl_Obj)
-        self.assertRaises(TypeError, _tkinter.TkttType)
-        self.assertRaises(TypeError, _tkinter.TkappType)
+        support.check_disallow_instantiation(self, _tkinter.Tcl_Obj)
+        support.check_disallow_instantiation(self, _tkinter.TkttType)
+        support.check_disallow_instantiation(self, _tkinter.TkappType)
 
 class BigmemTclTest(unittest.TestCase):