fix(monitoring): restore was failing to file dashboard file
fix(monitoring): restore was failing to file dashboard file

since #4627 the dashboard files now has random part to them
and the `show-monitor` command was failing

this fix only getting the first dashboard and doesn't handle
the case of restoring multiple dashboards (for operator multi
tenant runs)

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests