Jurors in New York's Howard Beach trial, deliberating for a fifth day, asked to hear again testimony by Josephine Riomayor, who testified last month that she saw two people standing along the Belt Parkway early on Dec. 20, 1986. Last week, the jury began deliberating the fate of four white teen-agers charged in what prosecutors said was a racial attack that led to the death on the highway of Michael Griffith, a black man. Defense attorneys maintain that one of the two men Riomayor saw was Griffith. If so, the testimony would counter the prosecution's theory that Griffith was chased to his death. However, prosecutors maintain Griffith was not one of the men whom Riomayor saw.