Fix license to use the "official" BSD wording

fabpot · fabpot · commit d1686608d502 · 2020-01-31T09:01:23.000+01:00
diff --git a/LICENSE b/LICENSE
@@ -1,7 +1,5 @@
 Copyright (c) 2009-2020 by the Twig Team.
 
-Some rights reserved.
-
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are
 met:
