fix the calculation of show_in_checklist_ac flag

there was an error in calculation of that flag in taxon_concepts_mview. it is not used at the moment (the checklist autocomplete uses the show_in_species_plus_ac flag). at this point the values of those 2 flags should be identical, but they will possibly diverge once the subspecies changes are applied to Species+ autocomplete. at which point it would be good to have the other flag working properly.