bug#75310: Eliminate obsolete alias warning

[Eli Zaretskii <eliz@gnu.org>]

> From: Yuan Fu <casouri@gmail.com>
> Date: Fri, 3 Jan 2025 23:33:25 -0800
> Cc: Peter Oliver <p.d.oliver@mavit.org.uk>,
>  75310@debbugs.gnu.org
> 
> > On Jan 3, 2025, at 7:27 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> Date: Fri, 3 Jan 2025 14:47:53 +0000 (GMT)
> >> From: Peter Oliver <p.d.oliver@mavit.org.uk>
> >> cc: 75310@debbugs.gnu.org
> >> 
> >> On Fri, 3 Jan 2025, Eli Zaretskii wrote:
> >> 
> >>> IOW, can you show a minimal recipe for reproducing the problem,
> >>> starting from "emacs -Q"?
> >> 
> >> $ src/emacs -Q --batch --eval "(progn (message emacs-version) (require 'cl) (require 'treesit))"
> >> 31.0.50
> >> Package cl is deprecated
> >> lisp/treesit.el: Warning: ‘loop’ is an obsolete alias (as of 27.1); use ‘cl-loop’ instead.
> > 
> > Thanks.
> > 
> > Yuan, I think it would be good to rename 'loop' there to some other
> > name, do you agree?
> 
> I would definitely agree. I’ve always used cl-loop (and now I try to not use it for new code). The only instance of “loop” I can find in treesit.el is in a named-let in treesit-transpose-sexps wriiten by Theo, and it’s not the CL loop but a local function defined by named-let. I wanted to rewrite it so it doesn’t use named-let because it’s not very readable, but tbh I haven’t find the time to understand that function well enough to rewrite it (because it’s not very readable :-)
> 
> It could be that only I can’t understand it, but code should be simple enough that even I can understand ;-)

Renaming the symbol is easy, and doesn't require you to understand the
code completely.  We don't have to use cl-loop.