gpui: Restore mouse cursor on window deactivation (#55155)

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable


Release Notes:

- N/A

crates/gpui/src/window.rs

@@ -1457,6 +1457,10 @@ impl Window {
             move |active| {
                 handle
                     .update(&mut cx, |_, window, cx| {
+                        if !active {
+                            cx.platform.set_cursor_style(CursorStyle::Arrow);
+                        }
+
                         window.active.set(active);
                         window.modifiers = window.platform_window.modifiers();
                         window.capslock = window.platform_window.capslock();