Wrong Json syntax error

### Tested versions

- Reproducible in: 4.3.rc3.mono

### System information

Godot v4.3.rc3.mono - Windows 10.0.19045

### Issue description

https://github.com/user-attachments/assets/84096e28-efeb-4051-95cd-b0d5562352ca

When I am writing a json file, a syntax error is highlighted without any indication. When I close the file and open it again, the error highlighting is still there. But after closing the file and saving another file and opening the json file again the error highlighting no longer appears.

### Steps to reproduce

I don't know how the unprompted syntax error is triggered, it just appears by chance during the writing process.
If this error occurs, it can be reproduced using the steps above.

### Minimal reproduction project (MRP)

N/A

No source file, test, or entry point is identified. Start by reproducing the unexplained JSON syntax highlighting in Godot 4.3.rc3.mono on Windows, then follow the reported close, save another file, and reopen sequence. Done means the highlighting behavior is consistent and the error state is correctly refreshed.

Written by the indexing model from the issue text.