I’ve done far more than that; I’ve disabled the feature entirely. It takes work and arkenfoxing, but it can be done. (I was addressing the default behavior.)
You cannot, as far as I know, change the greyed out prompt in the search bar for more than its first appearance, but as of now if I type something that’s not a valid URL and hit enter, it tells me it cannot find that site…in other words my typos don’t get sent to any search engine.