Python: Update 04-kernel-arguments-chat.ipynb (#5910)

InputVariable name should be changed from "input" to "user_input". But
in my test, Both works well.

chat_history.add_user_message(input_text) command should be after
kernel.invoke() function. Otherwise chat_history will include the
current new input_text in the prompt. It is not necessary.

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### Contribution Checklist

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- [ ] The code builds clean without any errors or warnings
- [ ] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
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raises no violations
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Co-authored-by: Eduard van Valkenburg <[email protected]>
Co-authored-by: Evan Mattson <[email protected]>

python/notebooks/04-kernel-arguments-chat.ipynb

@@ -140,7 +140,7 @@
                 "    name=\"chat\",\n",
                 "    template_format=\"semantic-kernel\",\n",
                 "    input_variables=[\n",
-                "        InputVariable(name=\"input\", description=\"The user input\", is_required=True),\n",
+                "        InputVariable(name=\"user_input\", description=\"The user input\", is_required=True),\n",
                 "        InputVariable(name=\"history\", description=\"The conversation history\", is_required=True),\n",
                 "    ],\n",
                 "    execution_settings=execution_settings,\n",
@@ -245,7 +245,6 @@
                 "async def chat(input_text: str) -> None:\n",
                 "    # Save new message in the context variables\n",
                 "    print(f\"User: {input_text}\")\n",
-                "    chat_history.add_user_message(input_text)\n",
                 "\n",
                 "    # Process the user message and get an answer\n",
                 "    answer = await kernel.invoke(chat_function, KernelArguments(user_input=input_text, history=chat_history))\n",
@@ -253,6 +252,7 @@
                 "    # Show the response\n",
                 "    print(f\"ChatBot: {answer}\")\n",
                 "\n",
+                "    chat_history.add_user_message(input_text)\n",
                 "    chat_history.add_assistant_message(str(answer))"
             ]
         },