No such key “antialiasing” in schema “org.gnome.settings-daemon.plugins.xsettings:GNOME”

Impact
------
A user that tries to install vanilla-gnome-default-settings (or its reverse dependency vanilla-gnome-desktop) gets a command line warning when updating packages that trigger the libglib2.0-0 dpkg trigger.

Test Case
---------
Enabled proposed updates
From a terminal, run
sudo apt install vanilla-gnome-default-settings
The install should complete without any warnings from the gschema override.

Where Problems Could Occur
--------------------------
I just copied the line from the ubuntu-settings package where it is moved to the GDM greeter schema.

Most users would have the ubuntu-settings package installed which sets this key anyway. (We copy all the settings just in case they don't have it installed.)

If it's wrong, the font display might be a little worse on the login screen.

Original Bug Report
-------------------
Hi,

each time I install or update a package that triggers the libglib2.0-0 dpkg trigger, I see the following error message displayed:

# apt upgrade
[...]
Processing triggers for libglib2.0-0:amd64 (2.68.4-1ubuntu1) ...
No such key “antialiasing” in schema “org.gnome.settings-daemon.plugins.xsettings:GNOME” as specified in override file “/usr/share/glib-2.0/schemas/20_vanilla-gnome-default-settings.gschema.override”; ignoring override for this key.

ProblemType: Bug
DistroRelease: Ubuntu 21.10
Package: vanilla-gnome-default-settings 20.04.1
Uname: Linux 5.15.1-051501-lowlatency x86_64
ApportVersion: 2.20.11-0ubuntu71
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: KDE
Date: Thu Nov 11 10:36:05 2021
PackageArchitecture: all
SourcePackage: ubuntu-gnome-default-settings
UpgradeStatus: Upgraded to impish on 2021-10-03 (38 days ago)