user-accounts: do not set the language twice

The act_user_set_language function is called twice as a result of
commit 96c0c0a, which is not necessary.

https://bugzilla.gnome.org/show_bug.cgi?id=703392

panels/user-accounts/um-user-panel.c

@@ -1115,8 +1115,6 @@ language_response (GtkDialog         *dialog,
                                 show_restart_notification (d, lang);
                 }
 
-                act_user_set_language (user, lang);
-
                 button = get_widget (d, "account-language-button");
                 name = gnome_get_language_from_locale (lang, NULL);
                 um_editable_button_set_text (UM_EDITABLE_BUTTON (button), name);