ci: Remove extraneous copy of ssh_known_hosts

This doesn't actually work, because the shell expands `~` to the value
of the `HOME` environment variable, but `ssh` ignores that variable and
reads from the path from the user's `passwd` entry.  Since managed hosts
all have certificates now, and the CA key is included in the global host
key database, individual host keys are not needed anymore anyway.

vars/applyConfigPolicy.groovy

@@ -53,8 +53,6 @@ def stageKinit() {
             sh 'kinit -kt "${KEYTAB}" jenkins@PYROCUFFLINK.BLUE'
         }
         sh 'rm -rf .fact-cache'
-        sh 'install -m u=rwx,go= -d ~/.ssh'
-        sh 'cp roles/ssh-hostkeys/files/ssh_known_hosts ~/.ssh/known_hosts'
     }
 }