[Accuracy diff No.50、134] Fix accuracy diff for paddle.prod API

[ooooo-create]

For this failed case

paddle.prod(Tensor([3, 5],"float32"), keepdim=True, )

In paddle, when axis is None, and keepdim is True, it will be a tensor with an element and keep input rank
But for the torch.prod api

if axis is None:
	result = torch.prod(x, dtype = dtype)

it will return a 0 dims Tensor

[paddle-bot]

Thanks for your contribution!

[cangtianhuang]

@ooooo-create o师傅请修改一下 pr 描述，这个修改是因为什么呀？

[ooooo-create]

@ooooo-create o师傅请修改一下 pr 描述，这个修改是因为什么呀？

感谢提醒~，已添加 pr 描述

[cangtianhuang]

LGTM