Update model_loader_and_viewer.adoc
Update model_loader_and_viewer.adoc

Fixed typo in image width.
jMonkeyEngine/wiki.jmonkeyengine.org,jMonkeyEngine/wiki.jmonkeyengine.org,jMonkeyEngine/wiki.jmonkeyengine.org,jMonkeyEngine/wiki.jmonkeyengine.org