cleanup: Remove spaces in object literals

We only adopted this style relatively recently, so there's a bit
more to adjust. Still, it's manageable and another step towards
getting rid of the legacy style.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2866>

js/ui/windowMenu.js

@@ -217,7 +217,7 @@ export class WindowMenuManager {
     constructor() {
         this._manager = new PopupMenu.PopupMenuManager(Main.layoutManager.dummyCursor);
 
-        this._sourceActor = new St.Widget({ reactive: true, visible: false });
+        this._sourceActor = new St.Widget({reactive: true, visible: false});
         this._sourceActor.connect('button-press-event', () => {
             this._manager.activeMenu.toggle();
         });