The Raiden Wizard sets up a Raiden node on top of Infura. Your project ID is used to authenticate your access to Infura.
Why do I need Infura?
The Raiden Wizard aims to make installing Raiden as easy as possible. By using Infura you don't have to worry about layer 1, that is running your own synced Ethereum node. You can simply access all testnets and the Ethereum mainnet through the API endpoints provided by Infura.