interest+data: convert to span

Update span-lite to commit 8f7935ff4e502ee023990d356d6578b8293eda74

Change-Id: I511bc3541e8ba683661bc69656e83088dd06e97a
diff --git a/tools/ndnsec/sign-req.cpp b/tools/ndnsec/sign-req.cpp
index 6151714..f4655af 100644
--- a/tools/ndnsec/sign-req.cpp
+++ b/tools/ndnsec/sign-req.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2021 Regents of the University of California.
+ * Copyright (c) 2013-2022 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -95,7 +95,7 @@
   certificate.setFreshnessPeriod(1_h);
 
   // set content
-  certificate.setContent(key.getPublicKey().data(), key.getPublicKey().size());
+  certificate.setContent(key.getPublicKey());
 
   // set signature-info
   SignatureInfo signatureInfo;