cleanup: Avoid unnecessary braces

Our coding style has always been to avoid braces when all blocks
are single-lines.

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/805

js/ui/background.js

@@ -269,9 +269,9 @@ var Background = GObject.registerClass({
 
         let i;
         let keys = Object.keys(this._fileWatches);
-        for (i = 0; i < keys.length; i++) {
+        for (i = 0; i < keys.length; i++)
             this._cache.disconnect(this._fileWatches[keys[i]]);
-        }
+
         this._fileWatches = null;
 
         if (this._timezoneChangedId != 0)