Update alphadecays.txt #8268

Job	Run time
classicmode_1d_3dgrid	5m 14s
classicmode_3d	7m 44s
kilonova_1d_1dgrid	4m 54s
kilonova_1d_3dgrid	5m 57s
kilonova_2d_2dgrid	6m 41s
kilonova_2d_2dgrid_barnesthermalisation	5m 42s
kilonova_2d_2dgrid_expansionopac	5m 2s
kilonova_2d_2dgrid_xcomgammaphotoion	5m 51s
kilonova_2d_3dgrid	7m 18s
nebular_1d_3dgrid	12m 18s
nebular_1d_3dgrid_limitbfest	13m 53s
combine_checksums	19s
	1h 20m 53s

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