REUTERS – Vivian Schiller said she was stepping down as Twitter Inc’s news head after nearly a year at the microblogging website, the latest executive exit from the company this year. The former NBC executive, who was responsible for acting as a liaison between Twitter and news organizations, will be handing over the reins to Adam Sharp, who leads the government and elections team, a Twitter spokeswoman told Reuters. In her parting tweets, Schiller said her departure would allow Twitter vice president of Global Media Katie Stanton to “reorganize” as she saw fit. (http://bit. …