fix trivial comment issue

src/lib/datasrc/rbtree.h

@@ -540,8 +540,7 @@ public:
         }
         return (ret);
     }
-
-
+    //@}
     /// \brief return the next node which is bigger than node
     ///
     /// Each node in the tree has down pointer pointing to its subdomains,
@@ -562,9 +561,6 @@ public:
     const RBNode<T>* nextNode(const RBNode<T>* node,
                               NodeChain<T>& node_path) const;
 
-
-    //@}
-
     /// \brief Get the total number of nodes in the tree
     ///
     /// It includes nodes internally created as a result of adding a domain