clean header file include

Change-Id: I5df52db13f964a92bba7cc8659ec6bcc222f5cbb
diff --git a/src/protocol-detail/challenge.hpp b/src/protocol-detail/challenge.hpp
index 1ff74fd..aafcd42 100644
--- a/src/protocol-detail/challenge.hpp
+++ b/src/protocol-detail/challenge.hpp
@@ -21,8 +21,7 @@
 #ifndef NDNCERT_PROTOCOL_DETAIL_CHALLENGE_HPP
 #define NDNCERT_PROTOCOL_DETAIL_CHALLENGE_HPP
 
-#include "../certificate-request.hpp"
-#include <ndn-cxx/encoding/block.hpp>
+#include "../request-state.hpp"
 
 namespace ndn {
 namespace ndncert {
@@ -30,7 +29,7 @@
 class CHALLENGE {
 public:
   static Block
-  encodeDataPayload(const CertificateRequest& request);
+  encodeDataPayload(const RequestState& request);
 };
 
 }  // namespace ndncert