fix: Use correct keys when parsing action URL and custom Attributes from notification response

[stigi]

The Android SDK was using outdated keys for both, actionUrl and customAttributes.

I've created a broadcast via the CLI that contains both, action-url and custom attributes:

magicbell broadcasts create --action-url "act://ion" --content "Via CLI" --title "Check this Broadcast" --custom-attributes '{custom:"Value"}' --recipients "hi@ullrich.is"

Here's the API response that clearly shows the names of the keys. I've updated the parser accordingly.

Test Plan

I was able to confirm in the debugger that the correct values arrive now.