Remove unused concrete.misc.seen_introduction config option
Remove unused concrete.misc.seen_introduction config option

avdevs/concrete5,matt9mg/concrete5,avdevs/concrete5,TimDix/concrete5,TimDix/concrete5,avdevs/concrete5,matt9mg/concrete5,matt9mg/concrete5,MichaelMaar/concrete5,MichaelMaar/concrete5,TimDix/concrete5,MichaelMaar/concrete5