Update OpenStackClient role list commands

This command is deprecated. The new command is role assignment list.

Change-Id: I8dba0be21d5af6751bea13d8ff29cd4b7589ab3e
diff --git a/doc/source/guides/multinode-lab.rst b/doc/source/guides/multinode-lab.rst
index c996f95..8751eb8 100644
--- a/doc/source/guides/multinode-lab.rst
+++ b/doc/source/guides/multinode-lab.rst
@@ -260,7 +260,7 @@
     openstack user create $NAME --password=$PASSWORD --project $PROJECT
     openstack role add Member --user $NAME --project $PROJECT
     # The Member role is created by stack.sh
-    # openstack role list
+    # openstack role assignment list
 
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