Dynamic tab bar height (#19076)

Tracking issue: https://github.com/zed-industries/zed/issues/18078

Release Notes:

- Change tab bar height according to `ui-density`

---------

Signed-off-by: Aaron Ruan <aaron212cn@outlook.com>

crates/workspace/src/pane.rs

@@ -2259,7 +2259,6 @@ impl Pane {
     fn render_tab_bar(&mut self, cx: &mut ViewContext<'_, Pane>) -> impl IntoElement {
         let focus_handle = self.focus_handle.clone();
         let navigate_backward = IconButton::new("navigate_backward", IconName::ArrowLeft)
-            .shape(IconButtonShape::Square)
             .icon_size(IconSize::Small)
             .on_click({
                 let view = cx.view().clone();
@@ -2272,7 +2271,6 @@ impl Pane {
             });
 
         let navigate_forward = IconButton::new("navigate_forward", IconName::ArrowRight)
-            .shape(IconButtonShape::Square)
             .icon_size(IconSize::Small)
             .on_click({
                 let view = cx.view().clone();