Brian Steinberg Senior TV EditorEach August typically brings with it news of changes in the cast at “Saturday Night Live.” This month carries instead brings a development related to one of the more prominent people behind the scenes of the NBC show.Lindsay Shookus, one of the top producers at “SNL” who has played a strong role in booking guests and dealing with talent issues, is leaving the program. In a post on Instagram Friday, Shookus revealed her intent to depart.“After 20 seasons at ‘Saturday Night Live’ (and 415 live shows – i counted!), I have decided to trade in the wild late night life and move on from the show,” she said in her post.