docs(telemetry): drop the phase number from a node-health row title

The row was titled after the rollout phase its metrics came from, a number
defined only in a planning folder outside the shipped tree. Grafana shows
this title to operators, so it named something no reader could look up.

docker/telemetry/grafana/dashboards/node-health.json

@@ -441,7 +441,7 @@
       "id": 8
     },
     {
-      "title": "--- Extended Metrics (Recovered from Phase 6) ---",
+      "title": "--- Extended Metrics ---",
       "type": "row",
       "gridPos": {
         "h": 1,