Since various months the default GNOME desktop will hide the icons in almost every menu items. This choice should reduce the clutter in the user interface and give it a more uniform and simpler looking.
Everyone who wants to restore the menu icons could execute a simple command in a terminal window:
gsettings set org.gnome.desktop.interface menus-have-icons true
The change is immediately applied and doesn’t require any restart.
To restore the default look by hiding the menu icons you could simply execute the following command:
gsettings set org.gnome.desktop.interface menus-have-icons false