Remove trailing whitespace in protobuf/LICENSE
diff --git a/protobuf/LICENSE b/protobuf/LICENSE
index ab3bfa0..7efe25f 100644
--- a/protobuf/LICENSE
+++ b/protobuf/LICENSE
@@ -1,4 +1,4 @@
-Copyright 2013, the Dart project authors. 
+Copyright 2013, the Dart project authors.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are