bpo-41521: Rename blacklist parameter to not_exported (GH-21824)

Rename "blacklist" parameter of test.support.check__all__() to
"not_exported".
diff --git a/Lib/test/test_configparser.py b/Lib/test/test_configparser.py
index 230ffc1..80a9f17 100644
--- a/Lib/test/test_configparser.py
+++ b/Lib/test/test_configparser.py
@@ -2128,8 +2128,7 @@
 
 class MiscTestCase(unittest.TestCase):
     def test__all__(self):
-        blacklist = {"Error"}
-        support.check__all__(self, configparser, blacklist=blacklist)
+        support.check__all__(self, configparser, not_exported={"Error"})
 
 
 if __name__ == '__main__':