* Con Ed reduces voltage in NY's Brooklyn, Bronx * Company, union still far apart in talks-union * Heat wave to bake New York through weekend By Scott DiSavino NEW YORK, July 6 (Reuters) - Contract talks between Consolidated Edison Inc and locked-out union workers concluded late Friday while replacement crews struggled to end brownouts in Brooklyn and the Bronx as New York City sweltered in a prolonged heat wave. A Con Ed spokesman confirmed the talks had ended late on Frid