Prefer std::variant in dataNode_/schemaNode_

Right now, I already got rid of using spirit alternative parser to parse
different types of nodes (leaf, container...), so no reason to use
boost::variant over std::variant.

Change-Id: I1f713427117d7135b8309b7129f3b025465a9f7d
diff --git a/src/ast_path.hpp b/src/ast_path.hpp
index f768461..b1b949c 100644
--- a/src/ast_path.hpp
+++ b/src/ast_path.hpp
@@ -10,8 +10,8 @@
 #include <boost/fusion/adapted/struct/adapt_struct.hpp>
 #include <boost/fusion/include/adapt_struct.hpp>
 #include <boost/fusion/include/std_pair.hpp>
-#include <boost/variant/variant.hpp>
 #include <map>
+#include <variant>
 #include <vector>
 
 #include "ast_values.hpp"
@@ -83,7 +83,7 @@
 
 struct schemaNode_ {
     boost::optional<module_> m_prefix;
-    boost::variant<container_, list_, nodeup_, leaf_, leafList_> m_suffix;
+    std::variant<container_, list_, nodeup_, leaf_, leafList_> m_suffix;
 
     schemaNode_();
     schemaNode_(decltype(m_suffix) node);
@@ -93,7 +93,7 @@
 
 struct dataNode_ {
     boost::optional<module_> m_prefix;
-    boost::variant<container_, listElement_, nodeup_, leaf_, leafListElement_, leafList_, list_> m_suffix;
+    std::variant<container_, listElement_, nodeup_, leaf_, leafListElement_, leafList_, list_> m_suffix;
 
     dataNode_();
     dataNode_(decltype(m_suffix) node);