[xdoctest][task 142] Reformat example code with google style in quantization/quant_int8_mkldnn_pass.py (#56239)

* [xdoctest][task 142] test=docs_preview

* Update python/paddle/static/quantization/quant_int8_mkldnn_pass.py

* Update python/paddle/static/quantization/quant_int8_mkldnn_pass.py

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Co-authored-by: NNyakku Shigure <sigure.qaq@gmail.com>