render_nodes: Use correct license text
-// This file was generated by gir (https://github.com/gtk-rs/gir)
-// from gir-files (https://github.com/gtk-rs/gir-files)
-// DO NOT EDIT
+// Copyright 2019, The Gtk-rs Project Developers.
+// See the COPYRIGHT file at the top-level directory of this distribution.
+// Licensed under the MIT license, see the LICENSE file or <http://opensource.org/licenses/MIT>
use BlendMode;
use RenderNode;
