Fix LICENSE.txt to appease github license detection

Author: jagerman

LICENSE.txt

@@ -1,11 +1,3 @@
-This program 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, either version 3 of the License, or
-(at your option) any later version.
-
-Copyright (c) 2021 The Oxen Project
-
-
                     GNU GENERAL PUBLIC LICENSE
                        Version 3, 29 June 2007