Reduce namespace nesting (ndn::ndncert -> ndncert)

Change-Id: I5b69a2c3673cccdf07ea0ba3a0e7181894328f47
diff --git a/src/detail/ca-storage.cpp b/src/detail/ca-storage.cpp
index a377c6c..24fe38f 100644
--- a/src/detail/ca-storage.cpp
+++ b/src/detail/ca-storage.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2017-2020, Regents of the University of California.
+/*
+ * Copyright (c) 2017-2021, Regents of the University of California.
  *
  * This file is part of ndncert, a certificate management system based on NDN.
  *
@@ -20,11 +20,10 @@
 
 #include "detail/ca-storage.hpp"
 
-namespace ndn {
 namespace ndncert {
 namespace ca {
 
-unique_ptr<CaStorage>
+std::unique_ptr<CaStorage>
 CaStorage::createCaStorage(const std::string& caStorageType, const Name& caName, const std::string& path)
 {
   CaStorageFactory& factory = getFactory();
@@ -41,4 +40,3 @@
 
 } // namespace ca
 } // namespace ndncert
-} // namespace ndn