Hotwire and window.Rails = require("@rails/ujs") : Do we delete this line and Rails.start() ?

Hi

With the recent updates to JSP which I've merged, I'm now trying to get things to work.

In  Chris Oliver 's video he says to remove the lines relating to rails/ujs. When I looked in application.js I see the following still exist:

// Rails functionality
window.Rails = require("@rails/ujs")

...

// Start Rails UJS
Rails.start()

Should these lines be deleted or do they serve a different purpose I can't work out?

Thanks