Fix autoplay controls for narrow screens

On narrow screens, the autoplay and step controls move from the left and right side of the main image to above it. However, the autoplay controls were slightly too wide, causing them to be positioned above the space reserved for them.

Pro tip: In Firefox, you can easily debug issues like this in *responsive design view* (Ctrl+Shift+M), where you can easily resize the web page without resizing the browser itself (keeping the dev tools at full width). There, to see the bug that this fixes, simply make the website narrow enough that the controls move to the top of the main view (happens at 1300px width, I think).