cleanup: Use consistent 4-space indent

This is another bit where we've made good progress, and just need
a final push to complete the transition.

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

js/ui/osdWindow.js

@@ -148,7 +148,7 @@ export class OsdWindowManager {
     constructor() {
         this._osdWindows = [];
         Main.layoutManager.connect('monitors-changed',
-                                   this._monitorsChanged.bind(this));
+            this._monitorsChanged.bind(this));
         this._monitorsChanged();
     }