Update sn3d.cc #8645

Job	Run time
classicmode_1d_3dgrid	7m 45s
classicmode_3d	7m 14s
kilonova_1d_1dgrid	4m 16s
kilonova_1d_3dgrid	4m 26s
kilonova_2d_2dgrid	6m 16s
kilonova_2d_2dgrid_barnesthermalisation	5m 7s
kilonova_2d_2dgrid_expansionopac	4m 25s
kilonova_2d_2dgrid_xcomgammaphotoion	5m 4s
kilonova_2d_3dgrid	6m 28s
nebular_1d_3dgrid	11m 19s
nebular_1d_3dgrid_limitbfest	13m 44s
combine_checksums	17s
	1h 16m 21s

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