bug#61374: 30.0.50; Wrong mark-sexp with tree-sitter

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 09 Feb 2023 01:19:52 +0100
> From:  Ergus via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Just trying tree-sitter with c++-mode is doing a wrong mark-sexp.
> 
> With this code:
> 
> {
>   vector<int> myvar;
> }
> 
> M-x c++-ts-mode
> 
> go to { and do C-M-SPC. The region marked goes from { up to > instead of
> the corresponding }

The problem is in forward-sexp (try C-M-f from the same place), which
C-M-SPC calls.  This problem exists only on master, where forward-sexp
was modified to call treesit-forward-sexp; on emacs-29 the behavior is
as expected.

CC'ing Yuan and Theo, who will probably find a fix in no time...

Thanks.