Brothers! Sisters! Have you heard the good news? This Sunday on NBC, the holiday covenant between broadcast television and viewer shall be fulfilled in all of its live glory and, if the hype is worth anything, shall mark the rebirth of a flagging trend. After you’ve had your fill of ham and Peeps, gather thy people upon the couch at 8 p.m. on Sunday, when unto us another musical will be given: Andrew Lloyd Webber’s “Jesus Christ Superstar Live in Concert.” Yea, there will be a great wave of tweeting surging across the land, along with shouts of joy and cackles of ridicule. You may be wondering why any televised live musical is worth your time these days. Who can blame you? Until NBC announced this special it was widely assumed the thrill of live musical theater on TV was gone. But once upon a time we flocked to it, particularly when Carrie Underwood starred as Maria in NBC’s December 2013 broadcast of “The Sound of Music Live!” Five years ago its success shocked the …