docs: correct default site example
docs: correct default site example

This handles ipv4 and ipv6.

[ci skip]
dokku/dokku,claytonbrown/dokku,dokku/dokku,progrium/dokku,dokku/dokku,claytonbrown/dokku,progrium/dokku,dokku/dokku,claytonbrown/dokku,progrium/dokku,dokku/dokku,dokku/dokku,claytonbrown/dokku,claytonbrown/dokku,progrium/dokku,progrium/dokku,progrium/dokku,dokku/dokku,claytonbrown/dokku,claytonbrown/dokku,progrium/dokku,dokku/dokku,progrium/dokku,claytonbrown/dokku