Fix compatibility with OTP 27

[whitfin]

It looks like OTP 27 changed the signature to add :ordered, so this will match on that going forward!

[derekkraan]

@whitfin is it possible to get this merged and incorporated into a release soon? See this issue in the Horde project.

[derekkraan]

I am still concerned about this piece of the code (also after this PR):

1. We are matching on an opaque type.
2. The catch-all can result in the same issue coming back if the underlying type changes shape again. It would be better if it simply errored imo.

[derekkraan]

Perhaps we can use :gb_trees.next/1 instead?

https://www.erlang.org/doc/apps/stdlib/gb_trees.html#next/1

[derekkraan]

There is one other place where this function is being used, which is likely dropping through to the catch-all case.

I've made an attempt at adjusting the code, but I discovered that the tests aren't passing on master. Going to leave this for today.

[bitwalker]

Closing this in favor of #37