Add scipy to test dependencies (#261) #1075

Job	Run time
linux-gallery-python3.13-optional	48s
linux-gallery-python3.9-minimum	48s
windows-gallery-python3.13-optional	2m 31s
windows-gallery-python3.9-minimum	1m 11s
linux-python3.13	2m 11s
linux-python3.13-optional	3m 32s
linux-python3.9-minimum	2m 14s
macos-python3.13	2m 16s
macos-python3.13-optional	5m 8s
macos-python3.9-minimum	3m 54s
windows-python3.13-optional	7m 48s
windows-python3.13	4m 25s
windows-python3.9-minimum	3m 3s
conda-linux-python3.13	2m 26s
conda-linux-python3.13-optional	5m 52s
conda-linux-python3.9-minimum	2m 41s
	50m 48s

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