Drop cheshire for clojure.data.json

[expez]

We've had some issues with cheshire in the past. It's also a library with a ton of dependencies compared to clojure.data.json which is entirely self-contained.

clojure.data.json recently went through a round of performance tuning and is now faster than cheshire on some payloads and within spitting distance on most others.

The big payload from clojars is read as edn and cheshire is only used on the comparatively small payloads for maven central. I expect this change to:

1. Making parse an insignificant amount faster
2. Make our jar smaller
3. Make it less likely that we cause dependency problems in the future