[3.13] pythongh-93096: Load doctests in test_itertools (pythonGH-131133) (python#131136)

pythongh-93096: Load doctests in `test_itertools` (pythonGH-131133)
(cherry picked from commit 15a8412)

Co-authored-by: donBarbos <donbarbos@proton.me>

Author: miss-islington

Lib/test/test_itertools.py

@@ -1,5 +1,6 @@
 import doctest
 import unittest
+import itertools
 from test import support
 from test.support import threading_helper, script_helper
 from itertools import *
@@ -2844,7 +2845,7 @@ def test_permutations_sizeof(self):
 
 
 def load_tests(loader, tests, pattern):
-    tests.addTest(doctest.DocTestSuite())
+    tests.addTest(doctest.DocTestSuite(itertools))
     return tests