Provide instructions on how to set-up an execution layer node instead of mentioning Infura but no alternatives

In the [checklist](https://launchpad.ethereum.org/en/checklist) for validators it *does not* recommend Infura, but it's the only name that appears. It makes easier for people to take the non-recommended route.

A good solution would be to include a link to the official [ethereum.org "How to Run a Node"](https://ethereum.org/en/run-a-node/) so readers are given an option to learn how they can provide an execution client for themselves without using a 3rd party service.