Rep. Cedric L. Richmond on Sunday night apologized for a joke he made at a media dinner about White House adviser Kellyanne Conway, who stirred controversy when a picture showed her kneeling on a sofa in the Oval Office as she took a picture of a group gathered there. Richmond’s joke, delivered at a Wednesday night awards dinner at which lawmakers of both parties delivered funny monologues, was interpreted by many as having sexual overtones, although the Louisiana Democrat insisted on Thursday morning that that wasn’t his meaning.