(2nd LD) Lee Se-dol to leave S. Korean pro Go players association

(ATTN: UPDATES 3rd para, CHANGES quotes in 4th para, ADDS more info throughout, photo)

SEOUL, May 19 (Yonhap) -- South Korean Go master Lee Se-dol, who is known for having faced Google's artificial intelligence (AI) program AlphaGo in the ancient boar