Create backup whitelist for docker-compose

scripts/Common/OS/backup.fish

@@ -32,7 +32,7 @@ function backupAction -V dir
         echo "For a seamless experience, please make sure that you are able to establish an unattended ssh connection using key authentication."
         echo
         echo "$(tput bold)This command should succeed without user interaction:$(tput sgr0)"
-        echo "ssh -o PasswordAuthentication=no -p $VALHALLA_BACKUP_SERVER_PORT $VALHALLA_BACKUP_SERVER true"
+        echo "ssh -o PasswordAuthentication=no -P $VALHALLA_BACKUP_SERVER_PORT $VALHALLA_BACKUP_SERVER true"
         read -P "Press enter once you're done: "
         echo
     end