Jennifer Maas TV Business Writer“This Is Us” said goodbye to Mandy Moore’s Rebecca Pearson Tuesday — and so did many, many NBC viewers.The second-to-last episode of the Dan Fogelman-created family drama drew a 0.95 rating in the advertiser-coveted adults 18-49 demographic and 5.3 million viewers, according to Live + Same Day ratings from Nielsen. That is the second-highest rated and second-most watched episode of the sixth and final season of “This Is Us.” The top episode in both categories was the Jan.