We hear that executives from the Voice's parent company flew in for today's massacre. Michael Musto, the Voice's nightlife columnist and most high profile remaining staffer, has been let go, as was rumored last week. (There had apparently been some talk of Musto's column hanging on in some form, but that does not seem to have worked out.) Also let go, sources tell us, was Robert Sietsema, the Voice's longtime food cr…