Update copyright

As per matrix-org/synapse#7565 (comment)

Author: dbkr

src/components/structures/RightPanel.js

@@ -1,9 +1,6 @@
 /*
-Copyright 2015, 2016 OpenMarket Ltd
-Copyright 2017 Vector Creations Ltd
-Copyright 2017, 2018 New Vector Ltd
 Copyright 2019 Michael Telatynski <[email protected]>
-Copyright 2019, 2020 The Matrix.org Foundation C.I.C.
+Copyright 2015 - 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.