After about 1900 broadcasts, 84-year-old opera lover George Jellinek is signing off his WQXR show. “New York is losing one of the oldest and best-loved facets of its opera life: after some 36 years, George Jellinek’s weekly radio program, “The Vocal Scene,” is going off the air. The final broadcast is tonight at 10 on WQXR-FM, where the show originated in October 1969. The first program was titled “Love in Opera.” Tonight’s finale will be called, appropriately enough, “Leave Taking” and will be devoted to operatic farewells and Mr. Jellinek’s own.”