gh-136535: Tests: Correct Py_TPFLAGS_MANAGED_DICT in test_class.py

The `Py_TPFLAGS_MANAGED_DICT` constant in `Lib/test/test_class.py`
was incorrectly set to (1 << 2) instead of the correct (1 << 4) from
object.h.

Author: ever0de

Lib/test/test_class.py

@@ -859,7 +859,10 @@ def __init__(self, arg):
 
 from _testinternalcapi import has_inline_values
 
-Py_TPFLAGS_MANAGED_DICT = (1 << 2)
+Py_TPFLAGS_MANAGED_DICT = (1 << 4)
+
+class NoManagedDict:
+    __slots__ = ('a',)
 
 class Plain:
     pass
@@ -873,6 +876,13 @@ def __init__(self):
         self.c = 3
         self.d = 4
 
+class TestNoManagedValues(unittest.TestCase):
+    def test_flags(self):
+        self.assertEqual(NoManagedDict.__flags__ & Py_TPFLAGS_MANAGED_DICT, 0)
+
+    def test_no_inline_values_for_slots_class(self):
+        c = NoManagedDict()
+        self.assertFalse(has_inline_values(c))
 
 class TestInlineValues(unittest.TestCase):