Fix red develop 1d25ebe8cd42

The merge lane found `develop` red at `1d25ebe8cd429b59c2c8bedaf385b101ad635e43` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_task_model.py::test_task_table_has_expected_columns` - `api-unit-dc-test` The whole gate log: artifact `14354` on lane task 12668. Make `develop` pass its full gate again. Open a PR as usual: the merge lane merges a PR that fixes some of these and adds no failure even while `develop` is red.

Pinned tasks.notify_when_done in test_task_table_has_expected_columns (the only api-unit-dc-test failure); test 30 passed, quick gate green. PR #7739 queued in merge lane.