Bug#1113776: Downstream Debian/Ubuntu patch breaks flatpak app listing in malcontent

[Jeremy Bícha]

Test Case
========
1. Follow the GNOME instructions at https://flatpak.org/setup/Debian
2. After restarting, open the GNOME Software app and install an app
from Flathub. I suggest Chess Clock, which is a GNOME Circle app that
is not yet packaged as a .deb for Debian
3. Open the (GNOME) Settings app. Navigate to System > Users. Unlock.
4. Click Add User. Fill in the name and user name. Make sure that
Administrator is not selected. Finish adding the user.
5. Open the Parental Controls app. Unlock.
6. Click Restrict Applications. The Flatpak app (Chess Clock) should
be in this list.

You'll likely need to log out and log back in after installing the
updated malcontent packages.

Thank you,
Jeremy Bícha