Former “Saturday Night Live” star Cecily Strong backed out of playing Rep. Elise Stefanik on the show this past weekend because she was “uncomfortable” with the heavily criticized cold-open sketch, sources confirm to The Post. Strong, 39, appeared as a guest in the dress rehearsal ahead of the live show, then changed her mind “last minute” about playing Stefanik in the sketch, which mocked last week’s congressional hearings on antisemitism on college campuses. Newcomer Chloe Troast replaced Strong on air. The opening sketch is always the last one to be written and Saturday’s was slightly rushed, according to sources. Indeed,...