primary-menu: Clarify whether Preferences should be in separate section
The mockup at https://developer.gnome.org/hig/stable/primary-menus.html does not match the mockup at https://gitlab.gnome.org/GNOME/Initiatives/wikis/App-Menu-Retirement
In particular, the HIG has a separator between Preferences and the Help/About section but the wiki does not.
Also, the wiki has "About Application" but the HIG does not but that's #11 (closed)
Other Info
For gedit 3.32, we ended up putting Preferences in its own section because there are plugins that add extra preferences menu items.
cc/ @aday