Legend of the Sea Devils is incredibly genial. As Jodie Whittaker's penultimate "Doctor Who" outing, it's terribly disappointing, but Whittaker's entire run has been disappointing. It's far from her fault; rather, it's showrunner Chris Chibnall (who also co-wrote this special) being exceptionally milquetoast. But this special is a look at how blandly acceptable Whittaker's recent…