Do not make malcontent-control user uninstallable using gui

Currently, malcontent-control is displayed in GNOME Software as "Parental Controls" and allows users to uninstall it. However, at least on Fedora, trying to uninstall it will result in gnome-shell being uninstalled as well (or will hopefully result in just an error since gnome-shell is a protected package, but I am not sure how PackageKit handles this).

This is caused by its AppData file not containing <compulsory_for_desktop>GNOME</compulsory_for_desktop>.

I will send a MR to fix this. Alternative solution would be to remove the AppData file.