js: Set BoxLayout orientation

Use new `orientation` property instead of `vertical`.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3614>

js/ui/status/keyboard.js

@@ -121,7 +121,9 @@ class InputSourceSwitcher extends SwitcherPopup.SwitcherList {
     }
 
     _addIcon(item) {
-        let box = new St.BoxLayout({vertical: true});
+        const box = new St.BoxLayout({
+            orientation: Clutter.Orientation.VERTICAL,
+        });
 
         const symbol = new St.Bin({
             style_class: 'input-source-switcher-symbol',