FIX(otel): use statefulset mode for metrics collector

- Change from deployment to statefulset mode
- Target Allocator requires statefulset (not deployment)

opentelemetry-collector/manifests/collector-metrics.yaml

@@ -6,7 +6,7 @@ metadata:
   name: otel-metrics
   namespace: opentelemetry
 spec:
-  mode: deployment
+  mode: statefulset
   replicas: 2
   image: otel/opentelemetry-collector-contrib:0.113.0
   serviceAccount: otel-collector