By JULIA CASTILLO     Mexico’s Indio beer brand was originally called Cuauhtémoc, in honor of the last Aztec emperor-warrior, who died at the hands of Spanish conqueror Hernán Cortéz.   Back then, Cuauhtémoc’s image appeared on the label. Launched in the 1880s, its name was changed in 1905 because customers began to ask for it as “the one with the Indian image” (“la del Indio,” in Spanish). For practical