correct the sample usage of diff_api.py  (#19248)
correct the sample usage of diff_api.py  (#19248)

* correct then sample command of diff_api.py to align with paddle_build.sh
chengduoZH/Paddle,PaddlePaddle/Paddle,PaddlePaddle/Paddle,luotao1/Paddle,chengduoZH/Paddle,PaddlePaddle/Paddle,luotao1/Paddle,tensor-tang/Paddle,luotao1/Paddle,chengduoZH/Paddle,luotao1/Paddle,luotao1/Paddle,PaddlePaddle/Paddle,PaddlePaddle/Paddle,tensor-tang/Paddle,PaddlePaddle/Paddle,luotao1/Paddle,chengduoZH/Paddle,PaddlePaddle/Paddle,luotao1/Paddle,chengduoZH/Paddle,tensor-tang/Paddle,tensor-tang/Paddle,tensor-tang/Paddle