update logcumsumexp_grad_kernel.cu #14231

Job	Run time
Clone-windows / Clone Paddle	1m 55s
Windows-OPENBLAS / Check bypass / Check bypass	4s
Windows-GPU / Check bypass / Check bypass	6s
Windows-Inference / Check bypass / Check bypass	7s
Windows-OPENBLAS / Build and test	49m 45s
Windows-GPU / Build and test	1h 30m 55s
Windows-Inference / Build and test	2h 1m 48s
	4h 24m 40s

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