fix chat_template

InternVL3 chat template fails on system messages with OpenAI content format

| vLLM | `0.22.1` |
| PyTorch | `2.11.0+cu129` |
| Transformers | `5.10.2` |

run vllm serve:
```bash
vllm serve /InternVL3-2B \
--trust-remote-code \
--host 0.0.0.0 \
--port 8000 \
--served-model-name internvl3-2b
```

when i crul serve such as:
```bash
curl http://my_servers_ip:8000/v1/chat/completions \
-H "Content-Type: application/json" \
-d '{
"model": "internvl3-2b",
"messages": [
{
"role": "system",
"content": "你是一个专业的导游。"
},
{
"role": "user",
"content": "请用三句话介绍一下杭州"
}
],
"temperature": 0.7,
"max_tokens": 256
}'
```

error such as:
can only concatenate str (not \"list\") to str

tokenizer_config.json

@@ -268,7 +268,7 @@
     "<|video_pad|>"
   ],
   "bos_token": null,
-  "chat_template": "{%- if messages[0]['role'] == 'system' %}{{- '<|im_start|>system\n' + messages[0]['content'] + '<|im_end|>\n' }}{%- else %}{{- '<|im_start|>system\n\u4f60\u662f\u4e66\u751f\u00b7\u4e07\u8c61\uff0c\u82f1\u6587\u540d\u662fInternVL\uff0c\u662f\u7531\u4e0a\u6d77\u4eba\u5de5\u667a\u80fd\u5b9e\u9a8c\u5ba4\u3001\u6e05\u534e\u5927\u5b66\u53ca\u591a\u5bb6\u5408\u4f5c\u5355\u4f4d\u8054\u5408\u5f00\u53d1\u7684\u591a\u6a21\u6001\u5927\u8bed\u8a00\u6a21\u578b\u3002<|im_end|>\n' }}{%- endif %}{% for message in messages %}{%- if messages[0]['role'] != 'system' or not loop.first %}{{'<|im_start|>' + message['role'] + '\n'}}{% if message['content'] is string %}{{ message['content'] }}{% else %}{% for content in message['content'] %}{% if content['type'] == 'image' %}{{ '<image>\n' }}{% elif content['type'] == 'video' %}{{ '<video>\n' }}{% elif content['type'] == 'text' %}{{ content['text'] }}{% endif %}{% endfor %}{% endif %}{{'<|im_end|>\n'}}{%- endif %}{% endfor %}{% if add_generation_prompt %}{{'<|im_start|>assistant\n' }}{% endif %}",
+  "chat_template": "{%- if messages[0]['role'] == 'system' %}{{- '<|im_start|>system\n' }}{% if messages[0]['content'] is string %}{{ messages[0]['content'] }}{% else %}{% for content in messages[0]['content'] %}{% if content['type'] == 'text' %}{{ content['text'] }}{% endif %}{% endfor %}{% endif %}{{- '<|im_end|>\n' }}{%- else %}{{- '<|im_start|>system\n\u4f60\u662f\u4e66\u751f\u00b7\u4e07\u8c61\uff0c\u82f1\u6587\u540d\u662fInternVL\uff0c\u662f\u7531\u4e0a\u6d77\u4eba\u5de5\u667a\u80fd\u5b9e\u9a8c\u5ba4\u3001\u6e05\u534e\u5927\u5b66\u53ca\u591a\u5bb6\u5408\u4f5c\u5355\u4f4d\u8054\u5408\u5f00\u53d1\u7684\u591a\u6a21\u6001\u5927\u8bed\u8a00\u6a21\u578b\u3002<|im_end|>\n' }}{%- endif %}{% for message in messages %}{%- if messages[0]['role'] != 'system' or not loop.first %}{{'<|im_start|>' + message['role'] + '\n'}}{% if message['content'] is string %}{{ message['content'] }}{% else %}{% for content in message['content'] %}{% if content['type'] == 'image' %}{{ '<image>\n' }}{% elif content['type'] == 'video' %}{{ '<video>\n' }}{% elif content['type'] == 'text' %}{{ content['text'] }}{% endif %}{% endfor %}{% endif %}{{'<|im_end|>\n'}}{%- endif %}{% endfor %}{% if add_generation_prompt %}{{'<|im_start|>assistant\n' }}{% endif %}",
   "clean_up_tokenization_spaces": false,
   "eos_token": "<|im_end|>",
   "errors": "replace",