remove m_ prefix

Change-Id: I67aa409174fcd3f8df477be8aa4efb8ca96cf012
diff --git a/src/detail/ca-configuration.cpp b/src/detail/ca-configuration.cpp
index d44b36b..7d27bfb 100644
--- a/src/detail/ca-configuration.cpp
+++ b/src/detail/ca-configuration.cpp
@@ -40,7 +40,7 @@
     NDN_THROW(std::runtime_error("No JSON configuration found in file: " + fileName));
   }
     caProfile = CaProfile::fromJson(configJson);
-  if (caProfile.m_supportedChallenges.size() == 0) {
+  if (caProfile.supportedChallenges.size() == 0) {
     NDN_THROW(std::runtime_error("At least one challenge should be specified."));
   }
   // parse redirection section if appears