fix(grid): there can only be one toolbar
fix(grid): there can only be one toolbar

closes https://github.com/aurelia-ui-toolkits/aurelia-kendoui-bridge/issues/520

aurelia-ui-toolkits/aurelia-kendoui-bridge,aurelia-ui-toolkits/aurelia-kendoui-bridge,aurelia-ui-toolkits/aurelia-kendoui-plugin,aurelia-ui-toolkits/aurelia-kendoui-plugin