don't include restbase-roots in restbase.yaml
This is a partial revert of I63b1d4ba384458 which created a new
admin group restbase-roots and tried to include that here.
But it broke puppet on all nodes including both restbase and cassandra.
"Conflicting value for admin::groups found in role cassandra"
Letting the group exist but not including it here until we figured out
how to properly solve that conflict, to unbreak puppet.
This was supposed to resolve T89366.