gpui: Remove use of use gpui::* in examples (#22311)

This PR removes the use of `use gpui::*` in the GPUI examples, as this
is not how consumers should be importing GPUI.

Release Notes:

- N/A

crates/gpui/examples/window_shadow.rs

@@ -1,15 +1,16 @@
-use gpui::*;
-use prelude::FluentBuilder;
+use gpui::{
+    black, canvas, div, green, point, prelude::*, px, rgb, size, transparent_black, white, App,
+    AppContext, Bounds, CursorStyle, Decorations, Hsla, MouseButton, Pixels, Point, ResizeEdge,
+    Size, ViewContext, WindowBackgroundAppearance, WindowBounds, WindowDecorations, WindowOptions,
+};
 
 struct WindowShadow {}
 
-/*
-Things to do:
-1. We need a way of calculating which edge or corner the mouse is on,
-    and then dispatch on that
-2. We need to improve the shadow rendering significantly
-3. We need to implement the techniques in here in Zed
-*/
+// Things to do:
+// 1. We need a way of calculating which edge or corner the mouse is on,
+//    and then dispatch on that
+// 2. We need to improve the shadow rendering significantly
+// 3. We need to implement the techniques in here in Zed
 
 impl Render for WindowShadow {
     fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
@@ -128,7 +129,7 @@ impl Render for WindowShadow {
                             div()
                                 .flex()
                                 .bg(white())
-                                .size(Length::Definite(Pixels(300.0).into()))
+                                .size(px(300.0))
                                 .justify_center()
                                 .items_center()
                                 .shadow_lg()