Fix reference links (#3239)

* fix broken reference links that's pointing to a page that doesn't exists

* Fix 2 broken links and use the correct format

---------

Co-authored-by: Chi Wang <wang.chi@microsoft.com>

website/docs/tutorial/conversation-patterns.ipynb

@@ -1559,7 +1559,7 @@
    "metadata": {},
    "source": [
     "The implementation of the nested chats handler makes use of the\n",
-    "[`register_reply`](../reference/agentchat/conversable_agent/#register_reply)\n",
+    "[`register_reply`](/docs/reference/agentchat/conversable_agent/#register_reply)\n",
     "method, which allows you to make extensive customization to\n",
     " `ConversableAgent`. The GroupChatManager uses the same mechanism to implement the group chat.\n",
     "\n",
@@ -1579,7 +1579,7 @@
     "\n",
     "In this chapter, we covered two-agent chat, sequential chat, group chat,\n",
     "and nested chat patterns. You can compose these patterns like LEGO blocks to \n",
-    "create complex workflows. You can also use [`register_reply`](../reference/agentchat/conversable_agent/#register_reply) to create new patterns.\n",
+    "create complex workflows. You can also use [`register_reply`](/docs/reference/agentchat/conversable_agent/#register_reply) to create new patterns.\n",
     "\n",
     "This is the last chapter on basic AutoGen concepts. \n",
     "In the next chatper, we will give you some tips on what to do next."