GraphBLAS: Fix error in SuiteSparsePolicy.cmake #536

Job	Run time
macos	17m 3s
mingw (MINGW64)	10m 53s
msvc (with OpenMP)	6m 45s
msvc (without OpenMP)	6m 28s
mingw (MINGW32)	12m 54s
ubuntu (gcc with CUDA with OpenMP)	8m 10s
mingw (CLANG64)	13m 21s
ubuntu (gcc without CUDA with OpenMP)	3m 15s
ubuntu (clang with CUDA with OpenMP)	8m 9s
mingw (CLANG32)	11m 15s
ubuntu (clang without CUDA with OpenMP)	4m 27s
ubuntu (gcc without CUDA without OpenMP)	3m 46s
	1h 46m 26s

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