Update LICENSE date

Author: xluciano

lib_xassert/LICENSE.txt

@@ -1,6 +1,6 @@
 Software Release License Agreement
 
-Copyright (c) 2014-2019, XMOS, All rights reserved.
+Copyright (c) 2014-2020, XMOS, All rights reserved.
 
 BY ACCESSING, USING, INSTALLING OR DOWNLOADING THE XMOS SOFTWARE, YOU AGREE TO BE BOUND BY THE FOLLOWING TERMS. IF YOU DO NOT AGREE TO THESE, DO NOT ATTEMPT TO DOWNLOAD, ACCESS OR USE THE XMOS Software.