“Shrinking” makes two smart moves to start Season 3. “If you see me sinking, pull me up.”Without knowing what “Shrinking” Season 3 has in store, Paul’s motto sounds like a good idea for the show’s health as much as Paul’s. There’s enough to work with in the unusually large cast to fill out season after season of misty-eyed comedy. The finale primed Season 3 to prove it, but “Shrinking” squanders its shot, mainly because — much like Jimmy himself — it can’t commit. You just have to choose it.”In the end, it’s a shame “Shrinking” doesn’t follow its own advice.