ssh/config does not accept an array of paths

`ssh -F` only accepts a single config file, and it's what we use for interactive commands, e.g. `kamal app logs --follow`.

lib/kamal/configuration/docs/ssh.yml

@@ -66,5 +66,5 @@ ssh:
   #
   # Set to true to load the default OpenSSH config files (~/.ssh/config,
   # /etc/ssh_config), to false ignore config files, or to a file path
-  # (or array of paths) to load specific configuration. Defaults to true.
+  # to load specific configuration. Defaults to true.
   config: true