windows: Avoid recording minimized position to database (#9407)

Minimizing window records strange position to DB. When Zed is restarted,
the window goes far away.
<img width="975" alt="image"
src="https://github.com/zed-industries/zed/assets/6465609/98dbab71-fdbb-4911-b41a-9c3e498e5478">

So I fixed.

Release Notes:

- N/A

crates/gpui/src/platform/linux/x11/window.rs

@@ -338,6 +338,11 @@ impl PlatformWindow for X11Window {
         false
     }
 
+    // todo(linux)
+    fn is_minimized(&self) -> bool {
+        false
+    }
+
     fn content_size(&self) -> Size<Pixels> {
         self.0.inner.borrow_mut().content_size()
     }