Remove cast to const from MergeMapCollection()

Author: azat

src/nodebuilder.cpp

@@ -76,15 +76,14 @@ void NodeBuilder::OnMapStart(const Mark& mark, const std::string& tag,
 
 void MergeMapCollection(detail::node& map_to, detail::node& map_from,
                         detail::shared_memory_holder& pMemory) {
-  const detail::node& const_map_to = map_to;
   for (auto j = map_from.begin(); j != map_from.end(); j++) {
     const auto & from_key = j->first;
     /// NOTE: const_map_to.get(*j->first) cannot be used here, since it
     /// compares only the shared_ptr's, while we need to compare the key
     /// itself.
     ///
     /// NOTE: get() also iterates over elements
-    bool found = std::any_of(const_map_to.begin(), const_map_to.end(), [&](const detail::node_iterator_value<const detail::node> & kv)
+    bool found = std::any_of(map_to.begin(), map_to.end(), [&](const detail::node_iterator_value<detail::node> & kv)
     {
         const auto & key_node = kv.first;
         return key_node->scalar() == from_key->scalar();