DOC: model update in 'Using OpenAI Functions' docs (#14486)

- **Description:** : 
I just update the openai functions docs to use the latest model (ex.
gpt-3.5-turbo-1106)
https://python.langchain.com/docs/modules/chains/how_to/openai_functions

The reason is as follow: 

After reviewing the OpenAI Function Calling official guide at
https://platform.openai.com/docs/guides/function-calling, the following
information was noted:

> "The latest models (gpt-3.5-turbo-1106 and gpt-4-1106-preview) have
been trained to both detect when a function should be called (depending
on the input) and to respond with JSON that adheres to the function
signature more closely than previous models. With this capability also
comes potential risks. We strongly recommend building in user
confirmation flows before taking actions that impact the world on behalf
of users (sending an email, posting something online, making a purchase,
etc)."

CC: @efriis

docs/docs/modules/chains/how_to/openai_functions.ipynb

@@ -85,8 +85,8 @@
     }
    ],
    "source": [
-    "# If we pass in a model explicitly, we need to make sure it supports the OpenAI function-calling API.\n",
-    "llm = ChatOpenAI(model=\"gpt-4\", temperature=0)\n",
+    "# For better results in OpenAI function-calling API, it is recommended to explicitly pass the latest model.\n",
+    "llm = ChatOpenAI(model=\"gpt-3.5-turbo-1106\", temperature=0)\n",
     "prompt = ChatPromptTemplate.from_messages(\n",
     "    [\n",
     "        (\n",