Demo crashes on Widgets screen

Unfortunately anyone wanting to check out the Textual demo will currently experience a crash on the Widgets screen.

- https://github.com/Textualize/textual/issues/5976

To reproduce:

- Install `textual-demo` with uv or pipx
- Press <kbd>w</kbd> for the Widgets screen

```python
AttributeError: 'tree_sitter.Query' object has no attribute 'captures'
```