Flaky test: tests/sentry/integrations/api/endpoints/test_organization_code_mappings.py::OrganizationCodeMappingsTest::test_basic_post_with_invalid_integrationId

Failing test: `tests/sentry/integrations/api/endpoints/test_organization_code_mappings.py::OrganizationCodeMappingsTest::test_basic_post_with_invalid_integrationId`
Sentry sha: 06f4fc3ff37f1db5884793078c11b706fa99c8f3
Run: https://github.com/getsentry/sentry/actions/runs/22287678550

```
tests/sentry/integrations/api/endpoints/test_organization_code_mappings.py:274: in test_basic_post_with_invalid_integrationId
assert response.status_code == 404, response.content
E AssertionError: b'{"id":"42","projectId":"4557680266641408","projectSlug":"bengal","repoId":"58","repoName":"example","integrationId":...ts":{}},"stackRoot":"/stack/root","sourceRoot":"/source/root","defaultBranch":"master","automaticallyGenerated":false}'
E assert 201 == 404
E + where 201 = .status_code
```

Start with tests/sentry/integrations/api/endpoints/test_organization_code_mappings.py::OrganizationCodeMappingsTest::test_basic_post_with_invalid_integrationId and reproduce the failure from the linked Actions run. Inspect why the request returns 201 with a code mapping instead of 404 for an invalid integrationId. Done means the test reliably receives the expected 404 and the relevant test passes.

Written by the indexing model from the issue text.