CI: Enable clippy on Windows (#8240)

Release Notes:

- N/A

crates/gpui/src/platform.rs

@@ -1,5 +1,7 @@
 // todo!(linux): remove
 #![cfg_attr(target_os = "linux", allow(dead_code))]
+// todo!("windows"): remove
+#![cfg_attr(windows, allow(dead_code))]
 
 mod app_menu;
 mod keystroke;
@@ -61,9 +63,10 @@ pub(crate) fn current_platform() -> Rc<dyn Platform> {
 pub(crate) fn current_platform() -> Rc<dyn Platform> {
     Rc::new(LinuxPlatform::new())
 }
+// todo!("windows")
 #[cfg(target_os = "windows")]
 pub(crate) fn current_platform() -> Rc<dyn Platform> {
-    todo!("windows")
+    unimplemented!()
 }
 
 pub(crate) trait Platform: 'static {

crates/gpui/src/platform/test/platform.rs

@@ -126,8 +126,9 @@ impl Platform for TestPlatform {
         #[cfg(target_os = "macos")]
         return Arc::new(crate::platform::mac::MacTextSystem::new());
 
+        // todo!("windows")
         #[cfg(target_os = "windows")]
-        todo!("windows")
+        unimplemented!()
     }
 
     fn run(&self, _on_finish_launching: Box<dyn FnOnce()>) {

crates/gpui/src/scene.rs

@@ -1,3 +1,6 @@
+// todo!("windows"): remove
+#![cfg_attr(windows, allow(dead_code))]
+
 use crate::{
     point, AtlasTextureId, AtlasTile, Bounds, ContentMask, Corners, Edges, EntityId, Hsla, Pixels,
     Point, ScaledPixels, StackingOrder,