Replace reference to unofficial sample code in Admin Guide w/ crw-samples

In the Admin Guide for CRW 2.10 https://access.redhat.com/documentation/en-us/red_hat_codeready_workspaces/2.10/html-single/administration_guide/index?lb_target=stage#a-workspace-example_crw we mention sample code from https://github.com/l0rd/nodejs-sample

Instead of this unofficial repo owned by Mario, we should include a sample devfile that uses an official crw-samples repo.

Suggestion: use this nodejs sample project instead, as it doesn't refer to a `master` branch.

• https://github.com/redhat-developer/codeready-workspaces/blob/crw-2-rhel-8/dependencies/che-devfile-registry/devfiles/04_nodejs-configmap/devfile.yaml -> https://github.com/crw-samples/nodejs-configmap/tree/12.x