A while back, JSON serialization for the API was changed to always

return ordered keys. This affected WebHooks, but the unit test was never

fixed up to account for this.
This change fixes up the expected WebHook payload, ordering the keys.

When I say "ordering," it's based on the json module's method of

ordering, which orders them before converting to strings, which is why

"null" (None) is first.

Unit tests pass.