MERGE ME PLS Changing the user dashboard test

This changes the step in the user dashboard test from "And I should not see "Oldest Series"" to "And I should not find "Oldest Series"". The step was failing intermittently on Travis (but not locally), and this change is either going to [a] fix it, [b] produce a better error that lets me see why it's failing, or [c] change absolutely nothing. Unfortunately, I don't know which of those is true, since I've run this thing about a dozen times and haven't been able to make it fail.