If you’ve been shocked by the drama on Lifetime’s “UnREAL,” you may want to brace yourself before watching the 20-minute short film that inspired it. “Sequin Raze” is an engrossing look at the darker side of reality television, anchored by a scene in which a disheveled producer on a “Bachelor”-esque dating show plays on the deepest insecurities of a contestant while trying to get her to open up about being dismissed by the show’s dashing suitor.