dashboards(ovn): adopt refreshed layout

Replace both dashboards with the updated versions exported from the
staging Grafana (pluginVersion 12.3.1). The new layout drops
references to labels that the exporter no longer emits (ovn_pid,
ovs_version, db_version, rundir) and is aligned with the current
ovn_info shape (nb_schema_version, sb_schema_version).

Author: lucadelmonte