For all of its wonderful jump-scares and nail-biting suspense, the scariest thing about Wes Craven’s “The People Under the Stairs,” which I starred in as The Stairmaster 30 years ago, may be that this kind of horror film — a progressive and diverse movie that starred a young African-American kid as the hero and heart of the story — is still the exception rather than the rule in Hollywood in 2021.To say that Wes Craven was ahead of his time when he made the Universal Studios cult-horror classic