DT-1173: fix double icon in task bar
requested to merge sergio-costas/gnome-software:DT-1173-fix-double-icon-in-task-bar-when-launching-gnome-software into snap-store-41
When launching gnome-software, a double icon is shown in the taskbar, because the "old" one is for "snap-store", although both programs, in the snap, are really the same binary.
This patch fixes this.