ci: license-scan's cargo deny step fails its night job (no continue-on-error) #2177

The license-scan job's raw step cargo deny check licenses bans sources carries continue-on-error: true: a check that runs and cannot fail (a third state, C324 #6). A deny finding therefore never fails the job and never files the night issue; only the NOTICE drift tripwire can.

Fix: remove continue-on-error from that step. license-scan is already night-only (schedule / workflow_dispatch) and ends with the night-issue step, so a deny finding fails the night job and opens or updates its one issue. license-scan is not a required check (rules on main require gate and workspace-test only), so no gate changes. Test: night_checks_off_pr_path.rs asserts no step in a night job carries continue-on-error.

Part of #2124.