MAINT: Fix failing tests

This fixes some test failures I was seeing on my machine. There are still 8 errors related to ProbPlot. I fixed some of them, assuming I knew where the kwargs needed to be passed on. I don't know this code well anymore, so I'm not sure what the other keyword in the tests should do for `ProbPlot.ppplot`. @phobson any chance you can take a look at this or explain what is expected here? It should be an easy fix.