Bob Pollard and Guided By Voices announced in April that their current tour, entitled The Electric Conclusion Tour would be there last ever, making Saturday’s gig at the 9:30 Club their last ever D.C. performance. DCist was on hand to chronicle this grand event, and needless to say, the band went out with a bang. At around 11:30 p.m., the crowd was treated to a video retrospective chronicling GBV’s 21 years together. And yes, most…