Remove unneeded left-click filtering in ListItem (#3643)

This PR removes the left-click filtering from the `on_click` handler for
`ListItem`s.

It's no longer needed after #3584.

Release Notes:

- N/A

crates/ui2/src/components/list/list_item.rs

@@ -171,13 +171,7 @@ impl RenderOnce for ListItem {
                             })
                     })
                     .when_some(self.on_click, |this, on_click| {
-                        this.cursor_pointer().on_click(move |event, cx| {
-                            // HACK: GPUI currently fires `on_click` with any mouse button,
-                            // but we only care about the left button.
-                            if event.down.button == MouseButton::Left {
-                                (on_click)(event, cx)
-                            }
-                        })
+                        this.cursor_pointer().on_click(on_click)
                     })
                     .when_some(self.on_secondary_mouse_down, |this, on_mouse_down| {
                         this.on_mouse_down(MouseButton::Right, move |event, cx| {