It's really happening: On Friday, Silicon Valley star Kumail Nanjiani posted a goodbye photo on Twitter just two weeks before the Season 6 premiere. It was announced in May that Silicon Valley would end with Season 6, bringing to a close the wild misadventures of tech bro Richard Hendricks (Thomas Middleditch) and his cohorts as the frequently beleaguered start-up Pied Piper. Nanjiani's Silicon Valley goodbye is sure to tug at the heartstrings of every fan of the series; I know it tugged at mine. The actor, who's been an integral part of the cast and brought …