Remove root via update I want to remove the root, i.e. unroot the phone Nexus 4. The automatic factory image downloader using Nexus toolkit takes ages (for some reason). I also read somewhere that updating your rooted phone removes the root. So How do I update a rooted android in order to remove the root?
You simply flash a factory image. That overwrites the /system partition completely, effectively removing root.

For where to obtain those images, please take a look at Where can I find stock or custom ROMs for my Android device?