Use super().__init__ instead of explicitly calling named super-class. (#9166)

* Use super().__init__ instead of explicitly calling named super-class.

* Fix unittest (typo fix).

certbot/tests/plugins/dns_common_test.py

@@ -133,7 +133,7 @@ class CredentialsConfigurationTest(test_util.TempDirTestCase):
 
         def __init__(self, *args, **kwargs):
             self.reset()
-            logging.Handler.__init__(self, *args, **kwargs)
+            super().__init__(*args, **kwargs)
 
         def emit(self, record):
             self.messages[record.levelname.lower()].append(record.getMessage())