Fix demo

Author: emilk

crates/egui/src/containers/panel.rs

@@ -476,7 +476,7 @@ impl Panel {
     /// // `.resizable(true)` on both panels enables drag-to-collapse + drag-to-expand:
     /// let collapsed = egui::Panel::top("top_collapsed")
     ///     .resizable(true)
-    ///     .exact_size(20.0);
+    ///     .default_size(20.0);
     /// let expanded = egui::Panel::top("top_expanded")
     ///     .resizable(true)
     ///     .default_size(120.0);

crates/egui_demo_lib/src/demo/panels.rs

@@ -94,7 +94,7 @@ impl crate::View for Panels {
             bottom,
             egui::Panel::bottom("bottom_panel_collapsed")
                 .resizable(true)
-                .exact_size(16.0),
+                .default_size(20.0),
             egui::Panel::bottom("bottom_panel_expanded")
                 .resizable(true)
                 .max_size(128.0),