There are two vacuums at the heart of the final installment of “The Crown,” which concludes this week with six episodes to round out its last season. The first is the death of Princess Diana (Elizabeth Debicki), whose final weeks, tragic car accident and funeral took up the entirety of the season’s first part, released last month. The second is the death of Queen Elizabeth II (Imelda Staunton), the series’ central subject. “The Crown” couldn’t capture the Queen’s 2022 passing on screen; creator Peter Morgan chose to end his magnum opus well before the present day. But the end of...