fix(grafana_sct_dashboard): clear default list flags
fix(grafana_sct_dashboard): clear default list flags

for some reason, `Normal` and `Warning` events
are being listed automatically, and it is
distubring the usage of Grafana, showing many
information in the charts while not required
(specially during screenshots).
disabling these options so we will have a clean
dashboard when opening it, as the ability
to re-set it, is in there.

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