Simplify #8668

Job	Run time
classicmode_1d_3dgrid	9m 18s
classicmode_3d	8m 25s
kilonova_1d_1dgrid	4m 34s
kilonova_1d_3dgrid	4m 25s
kilonova_2d_2dgrid	6m 10s
kilonova_2d_2dgrid_barnesthermalisation	4m 57s
kilonova_2d_2dgrid_expansionopac	6m 9s
kilonova_2d_2dgrid_xcomgammaphotoion	4m 44s
kilonova_2d_3dgrid	9m 35s
nebular_1d_3dgrid	11m 49s
nebular_1d_3dgrid_limitbfest	14m 25s
combine_checksums	17s
	1h 24m 48s

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