Fix OpenAI docs code example (#3003)

Author: DouweM

docs/models/openai.md

@@ -130,7 +130,7 @@ Image generation is not currently supported. If you need this feature, please co
 
 File search and Computer use can be enabled by passing an [`openai.types.responses.FileSearchToolParam`](https://github.com/openai/openai-python/blob/main/src/openai/types/responses/file_search_tool_param.py) or [`openai.types.responses.ComputerToolParam`](https://github.com/openai/openai-python/blob/main/src/openai/types/responses/computer_tool_param.py) in the `openai_builtin_tools` setting on [`OpenAIResponsesModelSettings`][pydantic_ai.models.openai.OpenAIResponsesModelSettings]. They don't currently generate [`BuiltinToolCallPart`][pydantic_ai.messages.BuiltinToolCallPart] or [`BuiltinToolReturnPart`][pydantic_ai.messages.BuiltinToolReturnPart] parts in the message history, or streamed events; please submit an issue if you need native support for these built-in tools.
 
-```python{title="file_search_tool.py"}
+```python {title="file_search_tool.py"}
 from openai.types.responses import FileSearchToolParam
 
 from pydantic_ai import Agent