Corrected keybinding for snapping, "s" -> "Ctrl"

tutorials/3d/introduction_to_3d.rst

@@ -159,7 +159,7 @@ Vector3,Color,etc.).
 
 Some useful keybindings:
 
--  To snap placement or rotation, press the "s" key while moving, scaling
+-  To snap placement or rotation, press the "Ctrl" key while moving, scaling
    or rotating.
 -  To center the view on the selected object, press the "f" key.