Cron readiness check should not cause automated updates to not run

So we had

  /**
   * The error-level interval between cron runs, in seconds.
   *
   * If cron runs less frequently than this, an error will be raised during
   * validation. Defaults to 24 hours.
   *
   * @var int
   */
  private const ERROR_INTERVAL = 86400;

  /**
   * The warning-level interval between cron runs, in seconds.
   *
   * If cron runs less frequently than this, a warning will be raised during
   * validation. Defaults to 3 hours.
   *
   * @var int
   */
  private const WARNING_INTERVAL = 10800;

in the code already. But we are only using the warning interval and issuing an error at that point. I've opened an MR to make the validator behave in the intended way.