If you think you'll never use the function, go to Preferences > Technology Previews and turn it off.
If you'd like to try it once, create a page and upload it. You'll never see the prompt again.
Thanks Steve, much appreciated.
It's odd that I can't just turn off the rollover. I may well want to use the function at some point in the future but I'm sure I'll be able to remember how to access it.
As Steve pointed out…if you publish anything it goes away…even a blank page.