On mobile, file actions were being displayed mostly off screen, to the right or left of the file attachment thumbnail. This change fixes things by displaying the file actions below the file thumbnail. We also make sure to hide the actions if the user opens the caption editor. Testing Done: - Tested using file actions on mobile and desktop. - Tested opening the caption editor while file actions are open. - Tested tapping and hovering on multiple different thumbnails, opening and closing file actions for each.