Twenty years after opening, this wooden roller coaster hiding in an Indiana cornfield remains an unexpected thrill.The Voyage & Thunderbird from the Corn Maze at Holiday World & Splashin’ Safari.Credit: Holiday World & Splashin' Safari“Oh—my—GOD! What—the—hell!”One second, I’m pinned to the side of my seat; the next, I’m almost ejected from it, with wooden track and steel lattices flying past me at what seems like the speed of light. Next to me,…