Track change in the service manual

See alphagov/government-service-design-manual@bf899a662b0e213af56d5b1122d258590a45072d.
Update service manual #version-68

https://github.com/alphagov/government-service-design-manual/compare/version-67...version-68
Merge pull request #147 from alphagov/service-manual-redirects

Track change in the service manual