As part of T304538: Clean up GrowthExperiments-related user_properties rows, we should remove the user property for the "seen" state of the tour popup for the new Impact module a short while after the feature has launched. N days after it's out of A/B testing, the only way to get the tour would be if you have registered your account before the A/B test ended but haven't visited your homepage in the last N days. For something like N>90, there seems to be little value in alerting the user to changes in an interface the previous state of which they probably don't remember anyway.

So, some time after the feature is enabled everywhere, we should remove all code related to the growthexperiments-tour-newimpact-discovery property, and probably delete the property itself from the DB.