Actually, you can edit the "Default Camera" Data (or whatever camera your current maps tileset uses) in the CAMERAS Data editor.
Change DISTANCE MAXIMUM and DISTANCE MINIMUM fields to the same number (whatever distance you want the camera to remain at) and the mouse wheel will no longer function as a zoom.)
OR/AND
Alter the ZOOM LEVELS field, and delete all the default data. This data controls at what level the zoom effect starts to tilt the angle of the camera.