Avoid using np.maximum_sctype (dropped in NumPy 2) #355

Job	Run time
ubuntu-py38-oldestdeps	1m 17s
macos-py310-astroscrappy11	1m 9s
ubuntu-py39	1m 17s
ubuntu-py39-bottleneck	1m 15s
ubuntu-py310	1m 27s
macos-py39	1m 15s
windows-py310	1m 12s
ubuntu-codestyle	20s
ubuntu-build_docs	1m 24s
ubuntu-py310-test-alldeps-devdeps	1m 25s
	12m 1s

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