fix(telemetry): Size the overlay traffic bar gauge for 20 bars

Match the panel height the operator settled on in Grafana (18 rows) so
all 20 ranked bars render without an inner scrollbar, and reflow the
Sync Diagnostics row and the panels below it accordingly.

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

@@ -732,7 +732,7 @@
       "description": "###### What this is:\n*All overlay traffic categories ranked by inbound bytes, giving an at-a-glance view of which message types consume the most receive bandwidth.*\n\n###### How it's computed:\n*Top categories by latest inbound byte value across all traffic categories. Each bar is labelled with its traffic category followed by the node identity; the shared `_bytes_in` suffix is dropped from the category name because the panel already reports inbound bytes.*\n\n###### Reading it:\n*The longest bars are the biggest bandwidth consumers; on a synced node transactions, proposals, and validations usually lead.*\n\n###### Healthy range:\n*workload-dependent.*\n\n###### Watch for:\n*A single ledger-data or fetch category dominating (ongoing sync) or an unexpected category topping the list.*\n\n###### Source:\n[OverlayImpl.cpp](https://github.com/XRPLF/rippled/blob/develop/src/xrpld/overlay/detail/OverlayImpl.cpp)\n\n###### Function:\n`OverlayImpl ctor (TrafficGauges)`",
       "type": "bargauge",
       "gridPos": {
-        "h": 12,
+        "h": 18,
         "w": 24,
         "x": 0,
         "y": 56
@@ -793,7 +793,7 @@
         "h": 1,
         "w": 24,
         "x": 0,
-        "y": 68
+        "y": 74
       },
       "id": 16,
       "panels": []
@@ -806,7 +806,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 69
+        "y": 75
       },
       "options": {
         "tooltip": {
@@ -910,7 +910,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 69
+        "y": 75
       },
       "options": {
         "tooltip": {
@@ -959,7 +959,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 77
+        "y": 83
       },
       "options": {
         "tooltip": {
@@ -1008,7 +1008,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 77
+        "y": 83
       },
       "options": {
         "tooltip": {
@@ -1085,7 +1085,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 85
+        "y": 91
       },
       "options": {
         "tooltip": {
@@ -1127,7 +1127,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 85
+        "y": 91
       },
       "options": {
         "tooltip": {
@@ -1169,7 +1169,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 93
+        "y": 99
       },
       "options": {
         "tooltip": {
@@ -1211,7 +1211,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 93
+        "y": 99
       },
       "options": {
         "tooltip": {
@@ -1267,7 +1267,7 @@
         "h": 8,
         "w": 12,
         "x": 0,
-        "y": 101
+        "y": 107
       },
       "options": {
         "tooltip": {
@@ -1309,7 +1309,7 @@
         "h": 8,
         "w": 12,
         "x": 12,
-        "y": 101
+        "y": 107
       },
       "options": {
         "tooltip": {