Update all 2011 dates to 2021.
diff --git a/upbc/common.h b/upbc/common.h
index a46d17a..1867ae0 100644
--- a/upbc/common.h
+++ b/upbc/common.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2011, Google LLC
+ * Copyright (c) 2009-2021, Google LLC
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without