Drop a navigation guard that never fired

[pleek91]

Description

Stacked on #807. No behaviour change — the code being removed never ran.

setPropsAndUpdateRoute held a guard meant to stop a superseded navigation from acting on props that arrived late:

const currentNavigationId = navigationId

propStore.setProps(to).then((response) => {
  if (currentNavigationId !== navigationId) {
    return
  }

navigationId is a parameter and is never reassigned, so the comparison was always false. It has been that way since it was introduced in ae08389, which set out to "prevent outdated props from triggering context errors" — a real problem the guard never actually prevented.

That job is now done properly: a navigation whose props are discarded returns ABANDONED, which #807 added along with the first test covering the behaviour. With the guard gone the parameter is unused, so it goes too.