Kendo UI Grid Disable editing to Default group

HTML

<link rel="stylesheet" href="http://cdn.kendostatic.com/2013.1.319/styles/kendo.common.min.css">
<link rel="stylesheet" href="http://cdn.kendostatic.com/2013.1.319/styles/kendo.default.min.css">
<script src="http://cdn.kendostatic.com/2013.1.319/js/kendo.web.min.js"></script>
<div id="grid"></div>

CSS

html {
    font:12px sans-serif;
}

span.k-icon.k-group-delete{
    display:block;
}

JavaScript

$("#grid").kendoGrid({
                        dataSource: {
                            type: "odata",
                            transport: {
                                read: "http://demos.kendoui.com/service/Northwind.svc/Orders"
                            },
                            group: [{field: "OrderID"}],
                            schema: {
                                model: {
                                    fields: {
                                        OrderID: { type: "number" },
                                        Freight: { type: "number" },
                                        ShipName: { type: "string" },
                                        OrderDate: { type: "date" },
                                        ShipCity: { type: "string" }
                                    }
                                }
                            },
                            pageSize: 20,
                            serverPaging: true,
                            serverFiltering: true,
                            serverSorting: true
                        },
                        height: 430,
                        filterable: true,
                        groupable: true,
                        sortable: true,
                        pageable: true,
                        columns: [{
                                field:"OrderID",
                                filterable: false,
                                groupable:false
                            },
                                  {field: "Freight",
                                   groupable:false},
                            {
                                field: "OrderDate",
                                title: "Order<br>Date",
                                width: 120,
                                format: "{0:MM/dd/yyyy}",
                                groupable:false
                            }, {
                                field:...