Cursor Lock Does Nothing on MacOS

## Bevy version

0.7.0

## Relevant system information

MacOS Macbook Pro 13" running on M1 processor

## What you did

```rs
fn lock_mouse(window: &mut Window) {
window.set_cursor_visibility(false);
window.set_cursor_lock_mode(true);

window.set_cursor_position(Vec2::new(window.width() / 2.0, window.height() / 2.0));
}
```

## What went wrong

- what were you expecting?
For this code to do both correctly, like it does on Windows.

- what actually happened?
On MacOS, this hides the cursor while it's in the window, but does not lock the cursor to the window.

## Additional information

This function is being called on a startup system. Doing it after, in a main system, doesn't work either.