bug#60296: The imenu is not created properly in c-ts-mode

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 60296-done@debbugs.gnu.org
> From: Yuan Fu <casouri@gmail.com>
> Date: Sat, 24 Dec 2022 19:00:21 -0800
> 
> > From: sniper <e190@163.com>
> > To: bug-gnu-emacs@gnu.org
> > Subject: 29.0.60; The imenu is not created properly in c-ts-mode.
> >
> > ``` c
> > char *test(int size){
> > return NULL;
> > }
> > ```
> > If c-ts-mode is enabled in a c file, the imenu created will be [` test(int size)`] if the return type of the function is a
> > pointer.
> > The expected display should just be the function name [` test `], with no subsequent arguments
> 
> Thanks, this should be fixed now.

This change leads to

  In c-ts-mode--fontify-declarator:
  progmodes/c-ts-mode.el:405:69: Warning: Unused lexical argument `args'

And "&rest args" is indeed unused there, AFAICT.