bug#80837: treesit-forward-comment off-by-one issue: overshoots by one character

reopen 80837
block 80837 by 31.1
thanks

>>>>>>>> I don't mind it being involved on master.
>>>>>>>> 
>>>>>>>> Do you propose to install  the patch you've just posted on emacs-31?
>>>>>>> 
>>>>>>> Yes.
>>>>>> 
>>>>>> To me this seems too involved for this stage of the freeze.
>>>>>> 
>>>>>> What do you think, Eli?
>>>>> 
>>>>> You mean, the patch in
>>>>> 
>>>>> https://lists.gnu.org/archive/html/bug-gnu-emacs/2026-07/msg00544.html
>>>>> 
>>>>> ?  Definitely too large, and introducing a new variable on top of
>>>>> that.
>>>> 
>>>> Right.  We're in agreement.
>>> 
>>> Cool, should I merge the patch to master then? 
>> 
>> Yes, please.
>
> Cool I pushed it, that should fix this report so I’m closing it.

I'm very sorry to reopen it, but we still have the same problem
in the emacs-31 release branch.  For example, try in c-ts-mode to
uncomment a comment, and it leaves the trailing */ comment endings.