References to d.o/cron, which is documentation for Drupal 7

There are a couple of references in Drupal core to https://www.drupal.org/cron. This is a redirect however to the Drupal 7 documentation on cron with url https://www.drupal.org/docs/7/setting-up-cron/overview.

We have two options here:

1. Update the documentation on d.o so that d.o/cron redirects to Drupal 8 documentation.
2. Update the links in Drupal core to https://www.drupal.org/docs/8/cron-automated-tasks.