Olivia Colman had “no idea” ‘Wicked Little Letters’ was based on a true story. The 50-year-old actress stars as Edith Swan in the drama film that follows the residents of a small town as they start receiving poison pen letters from an anonymous sender and was shocked to learn that the events depicted on screen had actually happened in real life. She told Collider: “I had no idea about the real story. When I was reading Jonny [Sweet]’s script, on the script, he had a black and white picture of Edith Swan and Rose Gooding, and I thought, “Wow, is this real?” And then, I Googled it and went, ‘Oh,…