Update config contract name

Seems like laravel renamed ```Illuminate\Contracts\Config\Config``` to ```Illuminate\Contracts\Config\Repository``` 

https://github.com/laravel/framework/tree/master/src/Illuminate/Contracts/Config

This will throw an error for a clean installation of Orchestra/Platform

Signed-off-by: Ahmad Shah Hafizan Hamidin <ahmadshahhafizan@gmail.com>