Update Geo setup guide to not delete private keys ever, only replace them

If you move those files and lose TCP connection you will never get access to the secondary node again
so let's just copy them instead ;)

doc/gitlab-geo/configuration.md

@@ -109,7 +109,7 @@ keys must be manually replicated to the secondary node.
 1. Make a backup of any existing SSH host keys:
 
     ```bash
-    find /etc/ssh -iname ssh_host_* -exec mv {} {}.backup.`date +%F` \;
+    find /etc/ssh -iname ssh_host_* -exec cp {} {}.backup.`date +%F` \;
     ```
 
 1. SSH into the **primary** node, and execute the command below:
@@ -118,7 +118,7 @@ keys must be manually replicated to the secondary node.
     sudo find /etc/ssh -iname ssh_host_* -not -iname '*.pub'
     ```
 
-1. For each file in that list copy the file from the primary node to
+1. For each file in that list replace the file from the primary node to
    the **same** location on your **secondary** node.
 
 1. On your **secondary** node, ensure the file permissions are correct: