doc: tweak wording on username/hostname stuff
doc: tweak wording on username/hostname stuff

lrytz/scala-jenkins-infra,adriaanm/scala-jenkins-infra,lrytz/scala-jenkins-infra,adriaanm/scala-jenkins-infra,scala/scala-jenkins-infra,scala/scala-jenkins-infra,retronym/scala-jenkins-infra,lrytz/scala-jenkins-infra,adriaanm/scala-jenkins-infra,retronym/scala-jenkins-infra,retronym/scala-jenkins-infra