Add missing preamble

Author: HosseinYousefi

pkgs/jni/lib/src/third_party/generated_bindings.dart

@@ -1,2 +1,6 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
 export 'global_env_extensions.dart';
 export 'jni_bindings_generated.dart';