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/HPOmen30LController/RGBController_HPOmen30L.cpp

@@ -4,7 +4,7 @@
 |   RGBController for HP Omen 30L                           |
 |                                                           |
 |   This file is part of the OpenRGB project                |
-|   SPDX-License-Identifier: GPL-2.0-only                   |
+|   SPDX-License-Identifier: GPL-2.0-or-later               |
 \*---------------------------------------------------------*/
 
 #include "RGBController_HPOmen30L.h"