Please add malcontent to the ubuntu-desktop packageset for noble

[Alessandro Astone]

Now that the ubuntu-desktop packageset is mostly up-to-date for 
questing, I wrote a little script to verify if the other stable release 
packagesets need updating too.
My script only found one source package missing in noble: malcontent.

malcontent was MIRd after the noble release, which I can see being a 
reason for why it was missed.
None of its binaries are pre-installed in Ubuntu Desktop, but they're 
seeded as 'supported' because some OEM configs pre-install it to comply 
with European regulations on parental controls.

Please add src:malcontent to the ubuntu-desktop packageset for noble, 
reflecting the fact that it is in main, primarily used in GNOME, and 
already in the ubuntu-desktop packageset for questing.