update notes about overall scores in objective evaluation

docs/leaderboard_objective.html

@@ -229,6 +229,7 @@ <h4>📝 Notes</h4>
           <ol>
             <li>Models labeled with 🌍 are API-Based models, while others are open-sourced.</li>
             <li>Some models are not optimized for correction and comparison critique dimensions, like Auto-J-13B and UltraCM-13B. Their scores are not recorded, and the overall scores are the average of other dimensions.</li>
+            <li>The details about how to compute the overall scores can be found in Section 4.3 in <a href="https://arxiv.org/abs/2402.13764">our paper</a>.</li>
           </ol>
         </p>
       </div>