Fix regressions introduced by flicker fix (#9162)

This pull request fixes a couple of easy regressions we discovered right
after using #9012 on nightly:

- Popover buttons for a chat message were being occluded by the message
itself.
- Scrolling was not working on the `List` element.

Release Notes:

- N/A

crates/collab_ui/src/chat_panel.rs

@@ -466,10 +466,6 @@ impl ChatPanel {
             .relative()
             .group("")
             .when(!is_continuation_from_previous, |this| this.pt_2())
-            .child(
-                self.render_popover_buttons(&cx, message_id, can_delete_message)
-                    .neg_mt_2p5(),
-            )
             .child(
                 div()
                     .group("")
@@ -583,6 +579,10 @@ impl ChatPanel {
                     )
                 },
             )
+            .child(
+                self.render_popover_buttons(&cx, message_id, can_delete_message)
+                    .neg_mt_2p5(),
+            )
     }
 
     fn has_open_menu(&self, message_id: Option<u64>) -> bool {