security: Rename security/v2/* to security/*

Security v1-v2 transition has been completed for a while and path
separation is no longer needed. However, this commit preserves
`ndn::security::v2` namespace, but makes it inline.

Some commonly used v2 headers are preserved, but are deprecated and
should be avoided in the dependent software.

Change-Id: I26056cb3d34bcdc0a16e06dea8c1a78c03da2d40
diff --git a/tests/unit/security/pib/pib-data-fixture.hpp b/tests/unit/security/pib/pib-data-fixture.hpp
index 21af850..66e65eb 100644
--- a/tests/unit/security/pib/pib-data-fixture.hpp
+++ b/tests/unit/security/pib/pib-data-fixture.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2018 Regents of the University of California.
+ * Copyright (c) 2013-2020 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -22,7 +22,7 @@
 #ifndef NDN_TESTS_UNIT_SECURITY_PIB_DATA_FIXTURE_HPP
 #define NDN_TESTS_UNIT_SECURITY_PIB_DATA_FIXTURE_HPP
 
-#include "ndn-cxx/security/v2/certificate.hpp"
+#include "ndn-cxx/security/certificate.hpp"
 
 namespace ndn {
 namespace security {
@@ -34,14 +34,14 @@
   PibDataFixture();
 
 public:
-  v2::Certificate id1Key1Cert1;
-  v2::Certificate id1Key1Cert2;
-  v2::Certificate id1Key2Cert1;
-  v2::Certificate id1Key2Cert2;
-  v2::Certificate id2Key1Cert1;
-  v2::Certificate id2Key1Cert2;
-  v2::Certificate id2Key2Cert1;
-  v2::Certificate id2Key2Cert2;
+  Certificate id1Key1Cert1;
+  Certificate id1Key1Cert2;
+  Certificate id1Key2Cert1;
+  Certificate id1Key2Cert2;
+  Certificate id2Key1Cert1;
+  Certificate id2Key1Cert2;
+  Certificate id2Key2Cert1;
+  Certificate id2Key2Cert2;
 
   Name id1;
   Name id2;