js: Adapt to GSettings API change

The 'schema' property has been deprecated for a long time. Even though
this will likely be reverted in glib, let's stop using it.

js/ui/components/telepathyClient.js

@@ -946,7 +946,7 @@ const ChatNotification = new Lang.Class({
 
         let format;
 
-        let desktopSettings = new Gio.Settings({ schema: 'org.gnome.desktop.interface' });
+        let desktopSettings = new Gio.Settings({ schema_id: 'org.gnome.desktop.interface' });
         let clockFormat = desktopSettings.get_string(CLOCK_FORMAT_KEY);
         let hasAmPm = date.toLocaleFormat('%p') != '';