DOC: Update copyright duration

Author: thclark

LICENSE

@@ -3,7 +3,7 @@ octue-sdk-python Application SDK for python-based apps on the Octue platform
 
 MIT License
 
-Copyright (c) 2017-2019 Octue Ltd
+Copyright (c) 2017-2021 Octue Ltd
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal