calendar: Unbind settings when destroying

Running dispose on the setting causes issues when we're being destroyed,
as the signal handler in the GSettings binding will be cleared by the
GObject itself before it has the chance, resulting in warnings.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1349>

js/ui/calendar.js

@@ -908,7 +908,7 @@ class DoNotDisturbSwitch extends PopupMenu.Switch {
             Gio.SettingsBindFlags.INVERT_BOOLEAN);
 
         this.connect('destroy', () => {
-            this._settings.run_dispose();
+            Gio.Settings.unbind(this, 'state');
             this._settings = null;
         });
     }