bug#34663: remove ftx font backend

[Eli Zaretskii]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: 34663@debbugs.gnu.org,  stefan@marxist.se
> Date: Tue, 07 Jan 2020 16:59:41 +0100
> 
>     >> Add an entry to NEWS on master that itʼs deprecated and will be
>     >> removed, and add verbiage to configure telling people to install cairo
>     >> development packages if XFT is detected. That means weʼd remove XFT in
>     >> emacs-29.
> 
>     Eli> But removing XFT basically means we are deprecating non-Cairo builds
>     Eli> on X.  Is that really what we want to do?
> 
> 'we' I donʼt know. 'I' have a very definite opinion :-)
> 
> How about I just start by flipping cairo on master?

Sure, that's definitely fine.