gpui: Fix TextStyle default font_family crash on Windows, use `Segoe UI` for Windows (#14040)

Release Notes:

- Fixed default font_family crash on Windows, use `Segoe UI`.

## Crash error message

```
thread 'main' panicked at crates\gpui\src\text_system.rs:150:9:
failed to resolve font 'Helvetica' or any of the fallbacks: 
Zed Plex Mono, Helvetica, Cantarell, Ubuntu, Noto Sans, DejaVu Sans
```