STAMFORD — Dec. 31 will mark the end of an era at NBC Sports Group. It will be the last day on the air for the Stamford broadcaster’s NBCSN cable channel. The programming of NBCSN, which is available in more than 75 million homes in the U.S., will be moving to other platforms owned by NBC Sports’ parent company NBCUniversal — including the cable USA Network and streaming service Peacock. The channel has operated since 1995 when it was founded as the Outdoor Life Network, and later renamed Versus, before taking its current name. In an interview this month with Hearst Connecticut Media Group, NBC Sports Chairman Pete Bevacqua discussed…