Bump ahash dependency version to 0.8.5

[joshlf]

The previous version had a bug, and was yanked.

[jonhoo]

Unfortunately ahash appears in the public API of flurry, so this would constitute a breaking change. We'll probably want to do a breaking change for flurry down the line, and then we should also bump ahash, but for now we'll leave it unless there's a critical problem 👍

[shisoft]

The old ahash used a feature stdsimd that was no longer available in nightly Rust. Leading flurry unable to compile under nightly. tkaitchuck/aHash#200

Please consider bump ahash to 0.8

[jonhoo]

Coming shortly with a major version bump to flurry in #121.
I've also masked the ahash types for 0.5.0 so that we won't be trapped behind a major version wall in the future 👍

[jonhoo]

Released in 0.5.0 🎉