Fix copyright
> Since this is a copy-and-paste of old text, I think the copyright year should match when the original text was written, which according to git was 2017.
-.. Copyright 2018-2019 New Vector Ltd
+.. Copyright 2017,2019 New Vector Ltd
..
.. Licensed under the Apache License, Version 2.0 (the "License");
.. you may not use this file except in compliance with the License.
