Correct how docker registry credentials are passed or documented

[RickMoynihan]

The docstring states credentials should be supplied like this:

https://github.com/juxt/pack.alpha/blob/9fd4a63ddeec3bedcbc819422de5a40ccb9eb8c9/src/juxt/pack/api.clj#L23-L25

However the opts on that api function are just passed directly into the jib namespace; and that expects the keys to be formatted like they are here:

https://github.com/juxt/pack.alpha/blob/9fd4a63ddeec3bedcbc819422de5a40ccb9eb8c9/src/juxt/pack/jib.clj#L163-L164

I'm happy to work up a patch for this; but it's unclear to me what the intention is.

A work around to pass to credentials is to just call api/docker with :to-registry-username and :to-registry-password set.

[SevereOverfl0w]

The documentation is correct, the code is wrong.