dra: enable prometheus to scarpe kubelets

Author: alaypatel07

config/jobs/kubernetes/sig-scalability/DRA/sig-scalability-periodic-dra.yaml

@@ -223,6 +223,8 @@ periodics:
               value: "default"
             - name: PROMETHEUS_APISERVER_SCRAPE_PORT
               value: "6443"
+            - name: PROMETHEUS_SCRAPE_KUBELETS
+              value: "true"
           resources:
             requests:
               cpu: "6"