Fix red develop 54ade235ffdb

The merge lane found `develop` red at `54ade235ffdbfde70afa3224483c2869390083d8` on its own: no queued PR merges until it is fixed. Failing (tests and gate stages): - `tests/test_cross_org_isolation.py::test_every_path_parameter_is_swept_or_named` - `api-unit-dc-test` The whole gate log: artifact `13529` on lane task 12118. 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.

Removed the stale legacy_id (its routes were retired in #7560) from the list of unswept route parameters in the cross-org isolation test. PR #7561 merged as 61af930 and the develop deploy run passed. Quick gate and test file (17 passed) green. Memory: none applied.