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/screenShield.js

@@ -103,7 +103,7 @@ export class ScreenShield extends Signals.EventEmitter {
 
         this._loginManager = LoginManager.getLoginManager();
         this._loginManager.connect('prepare-for-sleep',
-                                   this._prepareForSleep.bind(this));
+            this._prepareForSleep.bind(this));
 
         this._loginSession = null;
         this._getLoginSession();