fix(tools): add license for gen_header_for_bin_reduce.py in order to open source

GitOrigin-RevId: f310055a3cd3744b058a3f69d0e2ef36da3ca3c2

tools/gen_header_for_bin_reduce.py

 #!/usr/bin/env python3
 # -*- coding: utf-8 -*-
+# MegEngine is Licensed under the Apache License, Version 2.0 (the "License")
+#
+# Copyright (c) 2014-2020 Megvii Inc. All rights reserved.
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT ARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 
 import sys
 import re