Update copyright year (#401)

Author: github-actions[bot]

README.md

@@ -234,7 +234,7 @@ This means you should not decorate async test functions with
 
 ## Copyright and Terms of Use
 
-Copyright (C) 2019-<span actions:bind='current-year'>2022</span> NIWA & British Crown (Met Office) & Contributors.
+Copyright (C) 2019-<span actions:bind='current-year'>2023</span> NIWA & British Crown (Met Office) & Contributors.
 
 Cylc is free software: you can redistribute it and/or modify it under the terms
 of the GNU General Public License as published by the Free Software Foundation,