Add missing license header to doc/source/conf.py

Also drop "coding utf-8" which is implied by python3

Author: philpep

doc/source/conf.py

@@ -1,4 +1,14 @@
-# -*- coding: utf-8 -*-
+# 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.
 #
 # testinfra documentation build configuration file
 #