`compact` function sorts by probability

The docstring of `compact` states that result will be "sorted ascendingly according to values", but it seems like there is a `sortOn (Down . snd)` in the code that causes the result to actually be sorted in descending order of probability.

https://github.com/tweag/monad-bayes/blob/14faeb72ba7a043e28e8f350813b50d3397caa1b/src/Control/Monad/Bayes/Enumerator.hs#L94