edge: phosh: new icons showed up (GTK Demo, Icon Browser, Print Editor, Widget Factory)

Let's hide the new desktop icons by adjusting postmarketos-hidden-desktop-entries.

Note that the way the package currently works, this will only be in effect for new installations. To fix this, we need to rework the package to use replaces= and overriding the .desktop files from the Alpine packages, instead of placing overrides in /etc/skel (see #865 (closed)).