Incorrect highlighting with `variable`s

When quoted data is declared using the `variable` command, occurrence highlighting picks up a lot of irrelevant stuff.

<img width="391" height="78" alt="Image" src="https://github.com/user-attachments/assets/632b6658-3ac7-4b3e-84fd-ab159b3c2d58" />

### Lean version

```
Lean 4.22.0-rc3
Target: arm64-apple-darwin23.6.0 macOS
```

### `quote4` version

`867d9dc77534341321179c9aa40fceda675c50d4`