Flaky test: tests/sentry/monitors/consumers/test_monitor_consumer.py::MonitorConsumerTest::test_rate_limit

Failing test: `tests/sentry/monitors/consumers/test_monitor_consumer.py::MonitorConsumerTest::test_rate_limit`
Sentry sha: d9ad7639e47f7492cc115bef2a69b9f344529f4f
Run: https://github.com/getsentry/sentry/actions/runs/22300371327

```
tests/sentry/monitors/consumers/test_monitor_consumer.py:747: in test_rate_limit
self.send_checkin(
tests/sentry/monitors/consumers/test_monitor_consumer.py:111: in send_checkin
with self.check_processing_errors(wrapper, expected_error, expected_monitor_slug):
/opt/hostedtoolcache/Python/3.13.1/x64/lib/python3.13/contextlib.py:148: in __exit__
next(self.gen)
tests/sentry/monitors/consumers/test_monitor_consumer.py:144: in check_processing_errors
assert len(args_list) == 1
E assert 0 == 1
E + where 0 = len([])
```

Start with tests/sentry/monitors/consumers/test_monitor_consumer.py, especially test_rate_limit and the check_processing_errors path shown in the traceback. Reproduce the failure using the linked GitHub Actions run or the stated Sentry SHA, then identify why the expected processing error is absent. Done means the test is deterministic and passes reliably.

Written by the indexing model from the issue text.