Add scipy to test dependencies #1073

Job	Run time
conda-linux-python3.13	2m 21s
conda-linux-python3.13-optional	5m 43s
conda-linux-python3.9-minimum	2m 36s
linux-python3.13	2m 23s
linux-python3.13-optional	3m 33s
linux-python3.9-minimum	2m 16s
macos-python3.13	1m 25s
macos-python3.13-optional	3m 48s
macos-python3.9-minimum	3m 47s
windows-python3.13	4m 7s
windows-python3.13-optional	5m 47s
windows-python3.9-minimum	3m 20s
linux-gallery-python3.13-optional	57s
linux-gallery-python3.9-minimum	39s
windows-gallery-python3.13-optional	2m 28s
windows-gallery-python3.9-minimum	1m 6s
	46m 16s

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