cleanup: Remove trailing spaces

We generally avoid these (not least because Linus hates them enough
to make git complain loudly), but some sneaked in over time ...

https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/731

js/ui/keyboard.js

@@ -1081,7 +1081,7 @@ var Keyboard = class Keyboard {
                 this.hide();
         });
 
-        Meta.get_backend().connect('last-device-changed', 
+        Meta.get_backend().connect('last-device-changed',
             (backend, deviceId) => {
                 let manager = Clutter.DeviceManager.get_default();
                 let device = manager.get_device(deviceId);