Try to fix gpt example

[xinhuitian]

In examples/chDB_GPT.ipynb, the refine_query part should print the query str instead of answer I think?

Meanwhile, for many LLMs (I used Zhipu for test in this case), the generated result always contains a markdown code block syntax around the real sql, so maybe we can add two replace operations to remove this? The test result is shown as below:

[CLAassistant]

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[auxten]

Thanks for your contribution