fix(telemetry): Sync State axis label "State (0-4)" -> "Server State"

The 0-4 values now render as named states via value mappings, so the numeric
axis label is misleading. Rename to "Server State".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docker/telemetry/grafana/dashboards/ledger-data-sync.json

@@ -829,7 +829,7 @@
           "displayName": "${__field.labels.series} ${__field.labels.xrpl_ident}",
           "unit": "short",
           "custom": {
-            "axisLabel": "State (0-4)",
+            "axisLabel": "Server State",
             "spanNulls": 1800000,
             "insertNulls": false,
             "showPoints": "auto",