Update the "GUESS" json payloads for the Apple Event Parser with real ones

[zspencer]

As we worked on fleshing out support for the remaining IAP notification types (#23), we realized that we don't have payloads for most of them. We put in our best guesses, but I wanted to put a ticket in case anyone in the community has access to anonymized versions of the notification payload fixtures marked GUESS so we can make them play nicely.