Brooklyn- Al Goldstein, the outspoken pornographer, brought to a close this week his rancorous 20-month legal saga, in which he was accused of harassing a former employee over her decision to resign. Mr. Goldstein pleaded guilty to a minor offense below a misdemeanor for harassing his former assistant by, among other things, sending her unflattering depictions of her that had appeared in his sex magazine, Screw. Last year, Mr. Goldstein was convicted on five misdemeanor charges of aggravated harassment, but in July of this year, an appeals court panel unanimously reversed the verdict on the ground that Mr. Goldstein had been denied a fair trial. As part of a plea agreement, Mr. Goldstein apologized yesterday to his former assistant in court and was credited for the six days he spent in jail.