Re-land taffy 0.8.3 (#34939)

Re #34938
- **chore: Bump taffy to 0.8.3**
- **editor: Fix sticky multi-buffer header not extending to the full
width**


Release Notes:

- N/A

crates/editor/src/code_context_menus.rs

@@ -844,7 +844,7 @@ impl CompletionsMenu {
         .with_sizing_behavior(ListSizingBehavior::Infer)
         .w(rems(34.));
 
-        Popover::new().child(list).into_any_element()
+        Popover::new().child(div().child(list)).into_any_element()
     }
 
     fn render_aside(