bug#58021: 29.0.50; Remove old font.c code

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: manuel@ledu-giraud.fr,  58021@debbugs.gnu.org
> Date: Sat, 24 Sep 2022 11:25:38 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Would it help if we move that to the end of the file?
> >
> > My primary motivation for leaving this is to try to attract someone to
> > get involved in maintaining and developing font.c and fontset.c.
> > We've all but lost our only expert on this, and leaving this part of
> > Emacs without an active maintainer is bad for us.  I might even add a
> > comment there that encourages people to finish implementation of at
> > least some of that stuff, in the hope that this will bring on board
> > someone capable and motivated.
> 
> Adding some commentary to it to explain what the purpose of the code is
> (and why it hasn't been enabled) would be helpful, at least.

Now done.