Update alphadecays.txt #8280

Job	Run time
classicmode_1d_3dgrid	4m 35s
classicmode_3d	8m 8s
kilonova_1d_1dgrid	4m 56s
kilonova_1d_3dgrid	5m 5s
kilonova_2d_2dgrid	7m 1s
kilonova_2d_2dgrid_barnesthermalisation	5m 27s
kilonova_2d_2dgrid_expansionopac	5m 6s
kilonova_2d_2dgrid_xcomgammaphotoion	5m 29s
kilonova_2d_3dgrid	6m 54s
nebular_1d_3dgrid	11m 36s
nebular_1d_3dgrid_limitbfest	13m 48s
combine_checksums	18s
	1h 18m 23s

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