build: require boost >= 1.71.0

Refs: #5276
Change-Id: Ie428541639dcf1113acfb9e9d0a80f9be87d6cd3
diff --git a/tools/ndn-autoconfig/procedure.hpp b/tools/ndn-autoconfig/procedure.hpp
index 3f1f630..d9513ed 100644
--- a/tools/ndn-autoconfig/procedure.hpp
+++ b/tools/ndn-autoconfig/procedure.hpp
@@ -57,7 +57,7 @@
   void
   runOnce();
 
-  boost::asio::io_service&
+  boost::asio::io_context&
   getIoService()
   {
     return m_face.getIoService();