requirements: Drop direct dependency on mock.

mock is just a backport of the standard library’s unittest.mock now.

The SAMLAuthBackendTest change is needed because
MagicMock.call_args.args wasn’t introduced until Python
3.8 (https://bugs.python.org/issue21269).

The PROVISION_VERSION bump is skipped because mock is still an
indirect dev requirement via moto.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

tools/tests/test_check_rabbitmq_queue.py

@@ -1,4 +1,4 @@
-import mock
+from unittest import mock
 from unittest import TestCase
 
 from scripts.lib.check_rabbitmq_queue import (

tools/tests/test_zulint_custom_rules.py

@@ -1,6 +1,6 @@
 import os
 
-from mock import patch
+from unittest.mock import patch
 from unittest import TestCase
 
 from zulint.custom_rules import RuleList