update: ADR-24 names Ubuntu's apt-daily timer, not a cron job, as what updates the package lists.

ADR.md

@@ -606,18 +606,18 @@ upgrade restarts the process that starts it: the manager's postinst restarts
 `vpn-router-manager.service`, and the router's restarts `vpn-router-web` and `vpn-router-setup`. A
 child of the manager would be stopped with the manager's cgroup in the middle of dpkg, leaving
 packages half configured, and the manager's unit cannot run apt at all, since `ProtectSystem=strict`
-makes `/usr` and `/var/lib/dpkg` read-only. A cron job updates the package lists, so a release
-newer than its last run is not seen until the next one.
+makes `/usr` and `/var/lib/dpkg` read-only. Ubuntu's `apt-daily` timer updates the package lists
+twice a day, so a release newer than its last run is not seen until the next one.
 
 Decision: The manager starts the helper `/usr/lib/vpn-router-manager/upgrade` with `systemd-run` as
 the transient unit `vpn-router-manager-upgrade`, of its own cgroup and without a sandbox, and does
 not wait for it. The helper:
 
 - finishes an interrupted dpkg run with `dpkg --configure -a`;
-- runs `apt-get install --only-upgrade` of the two packages, non-interactive, keeping changed configuration files, with `needrestart` suspended, and waiting for the dpkg lock that the cron job may hold;
+- runs `apt-get install --only-upgrade` of the two packages, non-interactive, keeping changed configuration files, with `needrestart` suspended, and waiting for the dpkg lock that `apt-daily` or `unattended-upgrades` may hold;
 - records the state and the result in `/var/lib/vpn-router-manager/upgrade.json`, replaced by a rename, and the output in `upgrade.log`.
 
-A restarted manager reads them again. A state of running without an active unit is shown as interrupted. The manager reboots the router the same way, as a transient timer `vpn-router-manager-reboot` 5 seconds later, so the answer reaches the browser first. It checks for updates the same way too: Check update runs `apt-get update` in the transient unit `vpn-router-manager-check`, which touches apt's update stamp when it succeeds, so an admin need not wait for the cron job. Only members of `admins`, as the router's `/account` answers, may start any of them.
+A restarted manager reads them again. A state of running without an active unit is shown as interrupted. The manager reboots the router the same way, as a transient timer `vpn-router-manager-reboot` 5 seconds later, so the answer reaches the browser first. It checks for updates the same way too: Check update runs `apt-get update` in the transient unit `vpn-router-manager-check`, which touches apt's update stamp when it succeeds, so an admin need not wait for the `apt-daily` timer. Only members of `admins`, as the router's `/account` answers, may start any of them.
 
 Consequences: The fixed unit name allows one upgrade at a time. The page loses the manager and the
 router's web service for a while during an upgrade and reads again until they answer. Sessions