altTab: Remove down arrow when removing an app from switcher

The arrow of the removed app was still left in the list with the
visibility of the arrow still depending on the original list order. This
could either lead to apps with just one window now suddenly having a
down arrow or apps with multiple windows not having one. If the last
window in the list had a down arrow, it would have been displayed
outside the window switcher.

Fixes https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/2935

https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1340

js/ui/altTab.js

@@ -853,6 +853,9 @@ class AppSwitcher extends SwitcherPopup.SwitcherList {
         if (index === -1)
             return;
 
+        this._arrows[index].destroy();
+        this._arrows.splice(index, 1);
+
         this.icons.splice(index, 1);
         this.removeItem(index);
     }