fix(tiering): missing comma in dashboard json (#6150)

fix: missing comma in dashboard json, prevents importing to grafana

Author: goochs

tools/local/monitoring/grafana/provisioning/dashboards/dragonfly.json

@@ -2265,7 +2265,8 @@
       ],
       "title": "Master Replication memory",
       "type": "timeseries"
-    } {
+    },
+    {
       "datasource": {
         "type": "prometheus",
         "uid": "PBFA97CFB590B2093"