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

Change-Id: I5b69a2c3673cccdf07ea0ba3a0e7181894328f47
diff --git a/src/name-assignment/assignment-hash.hpp b/src/name-assignment/assignment-hash.hpp
index 83acc28..66d3984 100644
--- a/src/name-assignment/assignment-hash.hpp
+++ b/src/name-assignment/assignment-hash.hpp
@@ -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.
  *
@@ -23,7 +23,6 @@
 
 #include "assignment-func.hpp"
 
-namespace ndn {
 namespace ndncert {
 
 /**
@@ -34,12 +33,10 @@
 public:
   AssignmentHash(const std::string& format = "");
 
-  std::vector<PartialName>
+  std::vector<ndn::PartialName>
   assignName(const std::multimap<std::string, std::string>& params) override;
-
 };
 
 } // namespace ndncert
-} // namespace ndn
 
 #endif // NDNCERT_ASSIGNMENT_HASH_HPP