docs: update code-style rule 2.24

This commit also updates existing code to use the new format.

refs #4681

Change-Id: I88e62a34fc55a69cd01d74e80a7000c6cf4d7c2d
diff --git a/src/delegation-list.hpp b/src/delegation-list.hpp
index a5cf58a..656a485 100644
--- a/src/delegation-list.hpp
+++ b/src/delegation-list.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2017 Regents of the University of California.
+ * Copyright (c) 2013-2018 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -39,8 +39,7 @@
   class Error : public tlv::Error
   {
   public:
-    explicit
-    Error(const std::string& what);
+    using tlv::Error::Error;
 
     Error(const std::string& what, const std::exception& innerException);
   };