Change SPDX license identifier from GPL 2.0 only to GPL 2.0 or later, as the original LICENSE file includes an or later clause at the end so the file headers were incorrect

Controllers/MSIMysticLightController/MSIMysticLight162Controller/MSIMysticLight162Controller.cpp

@@ -7,7 +7,7 @@
 |   Adam Honse                                  06 Mar 2021 |
 |                                                           |
 |   This file is part of the OpenRGB project                |
-|   SPDX-License-Identifier: GPL-2.0-only                   |
+|   SPDX-License-Identifier: GPL-2.0-or-later               |
 \*---------------------------------------------------------*/
 
 #include <algorithm>