This seems to be a variation of this question: Chrome: remove URL from autocomplete which doesn't show up in history?
Since the old URL that's being suggested is a history item, the "arrow keys, then Shift+Delete" answer may suffice. Doing this will remove that suggestion from the autocomplete data altogether.
To do what you specifically asked for, promoting the new URL, you will have to edit Chrome's SQLite database, as explained in the first answer to that question. For locating the database: see here (click). (I have not tried this method myself, though.)
Another way to promote the new URL may be to bookmark it, but I've had mixed results with that.