Remove RSA1 keys as only SSH version 2 is used

docker/s6/openssh/setup

@@ -1,10 +1,6 @@
 #!/bin/sh
 
 # Check if host keys are present, else create them
-if ! test -f /data/ssh/ssh_host_key; then
-    ssh-keygen -q -f /data/ssh/ssh_host_key -N '' -t rsa1
-fi
-
 if ! test -f /data/ssh/ssh_host_rsa_key; then
     ssh-keygen -q -f /data/ssh/ssh_host_rsa_key -N '' -t rsa
 fi

docker/sshd_config

@@ -4,7 +4,6 @@ ListenAddress 0.0.0.0
 ListenAddress ::
 Protocol 2
 LogLevel INFO
-HostKey /data/ssh/ssh_host_key
 HostKey /data/ssh/ssh_host_rsa_key
 HostKey /data/ssh/ssh_host_dsa_key
 HostKey /data/ssh/ssh_host_ecdsa_key