Slim down `common.hpp`

Change-Id: Ic9843a1b9ffc5b5b1fa6062c8250ba28c6aaa898
diff --git a/tests/test-common.cpp b/tests/test-common.cpp
index 89a764c..91ebcd4 100644
--- a/tests/test-common.cpp
+++ b/tests/test-common.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2023,  Regents of the University of California,
+ * Copyright (c) 2014-2024,  Regents of the University of California,
  *                           Arizona Board of Regents,
  *                           Colorado State University,
  *                           University Pierre & Marie Curie, Sorbonne University,
@@ -27,7 +27,7 @@
 
 namespace ndn::tests {
 
-shared_ptr<Interest>
+std::shared_ptr<Interest>
 makeInterest(const Name& name, bool canBePrefix, std::optional<time::milliseconds> lifetime,
              std::optional<Interest::Nonce> nonce)
 {
@@ -40,7 +40,7 @@
   return interest;
 }
 
-shared_ptr<Data>
+std::shared_ptr<Data>
 makeData(const Name& name)
 {
   auto data = std::make_shared<Data>(name);