chore: update oel monitoring quickstart (#2218)

Author: nipsufn

docs/self-hosted/oel/monitoring/monitoring.mdx

@@ -66,7 +66,7 @@ grafana:
       name: Tempo
       type: tempo
       uid: demo_tempo
-      url: http://tempo.default.svc.cluster.local:3100
+      url: http://tempo.default.svc.cluster.local:3200
     - access: proxy
       jsonData:
         derivedFields: