Fix flaky test tests/test_api_keys.py::test_last_use_and_the_audit_trail_carry_the_key_never_the_secret

The merge lane saw `tests/test_api_keys.py::test_last_use_and_the_audit_trail_carry_the_key_never_the_secret` fail and then pass on a rerun of the same tree. - Test: `tests/test_api_keys.py::test_last_use_and_the_audit_trail_carry_the_key_never_the_secret` - Tree: `d52deac816d9b8b3fe208457ebd49dd436f8330f` - Lane task: 13219 - Flake record: 01a1a159-e16f-7130-9752-c146c01ed596 Make it deterministic; do not delete it unless it tests nothing.

Made the flaky api-keys audit-trail test deterministic: the clients are now entered, so capture tasks are no longer cancelled, and the test polls for the captured row. Reproduced with an injected delay (old test fails, new passes, 29/29). Quick gate green. PR #7854 queued in the merge lane.