A Randomized, Double-Blind, Placebo-Controlled Phase 3 Study Of Pembrolizumab (MK-3475) In Combination With Concurrent Chemoradiation Therapy Followed By Pembrolizumab With Or Without Olaparib (MK-7339), Compared To Concurrent Chemoradiation Therapy Alone In Participants With Actively Diagnosed Treatment-Naïve Limited-Stage Small Cell Lung Cancer (LS-SCLC)