Comedian Jenny Slate and director Gillian Robespierre have re-teamed to try to recreate the magic of their 2014 film “Obvious Child,” a smart and tender movie that was swept a bit under the rug by its misguided designation as “the abortion comedy.” The likable, lightweight “Landline” sees Slate playing Dana, a young woman who’s engaged and having mixed feelings about it; meanwhile, she and her more adventurous younger sister discover their dad is cheating on their mom .