Markdown json will cause the ledger information parse failed.

### What happened?

**Describe the bug**
When I use the `MagenticOneGroupChat` and gpt-4o to build something, found a little problem.
The `ORCHESTRATOR_PROGRESS_LEDGER_PROMPT` required the model_client output json format as below
```
Please output an answer in pure JSON format according to the following schema. 
The JSON object must be parsable as-is. 
DO NOT OUTPUT ANYTHING OTHER THAN JSON, AND DO NOT DEVIATE FROM THIS SCHEMA:

    {{
       "is_request_satisfied": {{
            "reason": string,
            "answer": boolean
        }},
        "is_in_loop": {{
            "reason": string,
            "answer": boolean
        }},
        "is_progress_being_made": {{
            "reason": string,
            "answer": boolean
        }},
        "next_speaker": {{
            "reason": string,
            "answer": string (select from: {names})
        }},
        "instruction_or_question": {{
            "reason": string,
            "answer": string
        }}
    }}
```
but the result is markdown format json like this and it will cause the team chat failed
```json
{
  "content": "```json {...}"
}
```

**To Reproduce**
MagenticGroupChat and gpt-4o

```
ERROR:src.da_agent_magentic:群聊执行失败: Failed to parse ledger information after multiple retries.
Traceback (most recent call last):
  File "/agent_demo/src/da_agent_magentic.py", line 100, in analyze_data_file
    await Console(team.run_stream(task=task_description))
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_agentchat/ui/_console.py", line 117, in Console
    async for message in stream:
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_agentchat/teams/_group_chat/_base_group_chat.py", line 499, in run_stream
    await self._runtime.send_message(
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_core/_single_threaded_agent_runtime.py", line 332, in send_message
    return await future
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_core/_single_threaded_agent_runtime.py", line 445, in _process_send
    response = await recipient_agent.on_message(
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_core/_base_agent.py", line 113, in on_message
    return await self.on_message_impl(message, ctx)
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_agentchat/teams/_group_chat/_sequential_routed_agent.py", line 67, in on_message_impl
    return await super().on_message_impl(message, ctx)
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_core/_routed_agent.py", line 485, in on_message_impl
    return await h(self, message, ctx)
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_core/_routed_agent.py", line 389, in wrapper
    return_value = await func(self, message, ctx)
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_agentchat/teams/_group_chat/_magentic_one/_magentic_one_orchestrator.py", line 186, in handle_start
    await self._reenter_outer_loop(ctx.cancellation_token)
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_agentchat/teams/_group_chat/_magentic_one/_magentic_one_orchestrator.py", line 283, in _reenter_outer_loop
    await self._orchestrate_step(cancellation_token=cancellation_token)
  File "/agent_demo/.venv/lib/python3.10/site-packages/autogen_agentchat/teams/_group_chat/_magentic_one/_magentic_one_orchestrator.py", line 353, in _orchestrate_ste
    raise ValueError("Failed to parse ledger information after multiple retries.")
```

**Expected behavior**
The output should just as the prompt requires, just pure json.
```json
{
  "content": "{...}"
}
```

**Additional context**

When the `ORCHESTRATOR_PROGRESS_LEDGER_PROMPT` prompt add the following content, the issue will not appear any more.
```
DO NOT OUTPUT MARKDOWN FORMAT JSON
```
It should like below
```
Please output an answer in pure JSON format according to the following schema. 
The JSON object must be parsable as-is. 
DO NOT OUTPUT ANYTHING OTHER THAN JSON, 
DO NOT OUTPUT MARKDOWN FORMAT JSON, 
AND DO NOT DEVIATE FROM THIS SCHEMA
...
```


### Which packages was the bug in?

Python AgentChat (autogen-agentchat>=0.4.0)

### AutoGen library version.

Python 0.5.6

### Other library version.

_No response_

### Model used

gpt-4o

### Model provider

OpenAI

### Other model provider

_No response_

### Python version

3.10

### .NET version

None

### Operating system

MacOS

Labels: needs-triage
State: closed