Fix license file

Author: silvanocerza

LICENSE.txt

@@ -1,17 +1,3 @@
-This file includes licensing information for serial-discovery
-
-Copyright (c) 2018-2021 ARDUINO SA (www.arduino.cc)
-
-The software is released under the GNU General Public License, which covers the main body
-of the serial-discovery code. The terms of this license can be found at:
-https://www.gnu.org/licenses/gpl-3.0.en.html
-
-You can be released from the requirements of the above licenses by purchasing
-a commercial license. Buying such a license is mandatory if you want to modify or
-otherwise use the software for commercial activities involving the Arduino
-software without disclosing the source code of your own applications. To purchase
-a commercial license, send an email to license@arduino.cc
-
                     GNU GENERAL PUBLIC LICENSE
                        Version 3, 29 June 2007