update pooltoy to follow best practices around handlers and msgServer

[okwme]

The SDK is replacing the handler with a message server pattern. Pooltoy already uses this pattern but for some reason the handler is still present. The logic of the handler is such that it will always throw an error, so it's really not doing anything at all. We should be able to get rid of it but it would be good to make sure that we follow the same form as other popular modules (like bank or gov).