Warning: This story contains spoilers from “Coming 2 America.”Of all the must-see musical moments in the long-awaited sequel “Coming 2 America,” which arrives Friday on Amazon Prime Video, perhaps the most memorable one belongs to the man himself: Eddie Murphy.Or make that Randy Watson.That’s right: The Jheri-curled crooner — one of several characters that Murphy played in addition to Prince Akeem in 1988’s “Coming to America” — is back for his encore 33 years after warbling “The Greatest Love