Removes "vertical" state from this element (reverses everything done
by {@link #setVertical}).
@private
function() {
        var me = this,
            cls = me.verticalCls;

        delete me.vertical;
        if (cls) {
            delete me.verticalCls;
            me.removeCls(cls);
        }

        // delete the inverted methods and revert to inheriting from the prototype 
        delete me.setWidth;
        delete me.setHeight;
        if (!Ext.isIE9m) {
            delete me.getWidth;
            delete me.getHeight;
        }

        // revert to inheriting styleHooks from the prototype
        delete me.styleHooks;
    }