gpui: Fix hide titlebar on Windows, with `titlebar: None` option (#13975)
Jason Lee
created
Release Notes:
- N/A
Ref the macOS Window:
When the `titlebar` is none, the titlebar should be hidden.
https://github.com/zed-industries/zed/blob/adaa4831766cde63b408909cf65cdeb1641e5888/crates/gpui/src/platform/mac/window.rs#L516-L528
```
cargo run -p gpui --example window_positioning
```
## Before

## After
<img width="466" alt="image"
src="https://github.com/zed-industries/zed/assets/5518/176ce4ea-14e9-44c8-8f2d-01e20ff3e543">