Unused routes in workhorse

Within the workhorse routes a ciAPIPattern is being defined which is not in use any more.

As far as i understood we do not support the /ci/api any more so I think the routes using the ciAPIPattern should be removed. Namely those are:

route("", ciAPIPattern+`v1/builds/register.json\z`, ciAPILongPolling)

and

route("POST", ciAPIPattern+`v1/builds/[0-9]+/artifacts\z`, contentEncodingHandler(artifacts.UploadArtifacts(api, proxy)))