plugin android: removed comment on vibrator bug as it is fixed in dev version of plyer

sat/plugins/plugin_misc_android.py

@@ -246,8 +246,6 @@ class AndroidPlugin(object):
                 try:
                     vibrator.vibrate()
                 except Exception as e:
-                    # FIXME: vibrator is currently not working,
-                    # cf. https://github.com/kivy/plyer/issues/509
                     log.warning("Can't use vibrator: {e}".format(e=e))
         return mess_data