Revert "Add gnome-backgrounds"
Revert "Add gnome-backgrounds"

This reverts commit ae98f452ec52bb2ae97c06840f0b38a3797ad127.  We
already have it!

vrutkovs/vrutkovs.github.io,chergert/gnome-continuous,GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,chergert/gnome-continuous,chergert/gnome-continuous,vrutkovs/vrutkovs.github.io,GNOME/gnome-ostree,GNOME/gnome-ostree