A federal grand jury indicted two Dorchester men on charges of robbing and shooting an on-duty postal worker in the neighborhood in December. The indictment against Keyon A. Taylor and Maurice William Miner-Gittens, both in their early 20s, was handed up Thursday in federal court in Boston, records show. They are charged with several violations, including robbery and attempted robbery of a federal employee and use of a firearm. The postal worker was shot in the wrist during a scuffle in the back of his truck on Bailey Street.Travis Andersen can be reached at firstname.lastname@example.org. Follow him on Twitter @TAGlobe.