Before D.C. had a Krispy Kreme, Washingtonians in search of a freshly made doughnut could depend on the two branches of Heller’s Bakery. They may not have had the cachet of former White House pastry chef Ann Amernick’s mythical creations or the zen-like simplicity of Colorado Kitchen’s bucket o’ holes, but Heller’s doughnuts were nothing to scoff at. After the Tenleytown location closed a few years ago, Heller’s fans began to worry, but the Mt….