add copyright header to file

Summary: `wa_raft_header.hrl` was missing a copyright header, which opened this task T230770473

Reviewed By: jaher

Differential Revision: D78280624

fbshipit-source-id: 06de8e59c8d0cd3d18d825a7940506b3952cd719

Author: Adarsh Patel

include/wa_raft_logger.hrl

@@ -1,3 +1,9 @@
+%%% Copyright (c) Meta Platforms, Inc. and affiliates. All rights reserved.
+%%%
+%%% This source code is licensed under the Apache 2.0 license found in
+%%% the LICENSE file in the root directory of this source tree.
+%%%
+
 -include_lib("kernel/include/logger.hrl").
 
 -define(RAFT_LOG_OPTS, #{domain => [whatsapp, wa_raft]}).