The era of Jewish boxers — tough guys from the ghettos, like Benny Leonard and Barney Ross — is over. For that matter, the era of boxing itself, once king of all American sports, has passed, as well. In that regard, Dmitriy Salita is doubly a throwback, being both Jewish and a boxer, with an added twist: As a practicing Orthodox Jew, he does not fight on the Sabbath. What normally might be a potentially fatal limitation for a boxer (many fights are scheduled for weekend nights) has proved to be a public relations bonanza for this undefeated junior welterweight, now the star of Jason Hutt\’s documentary film, \”Orthodox Stance,\” opening April 11 in Los Angeles.