[AIRFLOW-2779] Make GHE auth third party licensed (#3803)

This reinstates the original license.

Author: ashb

LICENSE

@@ -220,6 +220,7 @@ at licenses/LICENSE-[project].txt.
     (ALv2 License) hue (https://github.com/cloudera/hue/)
     (ALv2 License) jqclock (https://github.com/JohnRDOrazio/jQuery-Clock-Plugin)
     (ALv2 License) bootstrap3-typeahead (https://github.com/bassjobsen/Bootstrap-3-Typeahead)
+    (ALv2 License) airflow.contrib.auth.backends.github_enterprise_auth
 
 ========================================================================
 MIT licenses

NOTICE

@@ -13,6 +13,11 @@ is subject to the terms and conditions of their respective licenses.
 See the LICENSE file for a list of subcomponents and dependencies and
 their respective licenses.
 
+airflow.contrib.auth.backends.github_enterprise_auth:
+-----------------------------------------------------
+
+* Copyright 2015 Matthew Pelland (matt@pelland.io)
+
 hue:
 -----
 This product contains a modified portion of 'Hue' developed by Cloudera, Inc.

airflow/contrib/auth/backends/github_enterprise_auth.py

@@ -1,21 +1,19 @@
 # -*- coding: utf-8 -*-
 #
-# Licensed to the Apache Software Foundation (ASF) under one
-# or more contributor license agreements.  See the NOTICE file
-# distributed with this work for additional information
-# regarding copyright ownership.  The ASF licenses this file
-# to you under the Apache License, Version 2.0 (the
-# "License"); you may not use this file except in compliance
-# with the License.  You may obtain a copy of the License at
+# See the NOTICE file distributed with this work for additional information
+# regarding copyright ownership.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
 #   http://www.apache.org/licenses/LICENSE-2.0
 #
-# Unless required by applicable law or agreed to in writing,
-# software distributed under the License is distributed on an
-# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
-# KIND, either express or implied.  See the License for the
-# specific language governing permissions and limitations
-# under the License.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 import flask_login
 
 # Need to expose these downstream