I have been looking for the option using the google app itself, but when selecting the settings button inside, it does nothing, only stays in the same screen without the options in the second and third panel.
So I dont know how to delete the bar on the main screen.
UPDATE
Besides the method that changes the launcher (that I havent tested yet), all the methods suggesting to disable google app or google search does not work because it does not uninstall or force the stop of the google app/google search inside the installed apps. So the idea its changed to how to disable google app in oreo 8.1.0.