NBC’s “Saturday Night Live” chose Pete Davidson to portray embattled Rep. Matt Gaetz — despite the cast member dating an 18-year-old last year.Davidson, 27, appeared as Gaetz (R-Fl.) in the show’s cold open, in which the 38-year-old lawmaker was featured as a guest on a Britney Spears-hosted talk show for “the social pariahs of the week.”