[release-5.7] Default configuration is not restored under loki config after RulerConfig deletion

$ oc get RulerConfig -n openshift-logging
No resources found in openshift-logging namespace.
$oc get cm/lokistack-dev-config -n openshift-logging
runtime-config.yaml (overrides) after deletion
overrides:
  application:
    ruler_alertmanager_config:
      alertmanager_url: https://_web._tcp.alertmanager-operated.openshift-user-workload-monitoring.svc
      enable_alertmanager_v2: true
      enable_alertmanager_discovery: true
      alertmanager_refresh_interval: 1m
      alertmanager_client:
        tls_ca_path: /var/run/ca/alertmanager/service-ca.crt
        tls_server_name: alertmanager-user-workload.openshift-user-workload-monitoring.svc.cluster.local
        type: Bearer
        credentials_file: /var/run/secrets/kubernetes.io/serviceaccount/token
      alert_relabel_configs:
      -
        source_labels: ["severity","project"]
        regex: warning;my-app-1
        action: replace
        separator: ;
        replacement: uwmlogs
        target_label: project
config.yaml after deletion
ruler:
  enable_api: true
  enable_sharding: true
  evaluation_interval: 1m
  poll_interval: 1m
  external_labels:
    environment: prod
    region: us-east-1
  .....