refactor: remove k8s and use release name for instance

!8

templates/PrometheusRule-thanos.yaml

@@ -6,11 +6,12 @@ kind: PrometheusRule
 metadata:
   labels:
     app.kubernetes.io/component: metrics
+    app.kubernetes.io/instance: {{ $.Release.Name }}
     app.kubernetes.io/name: thanos
     app.kubernetes.io/part-of: {{  $.Chart.Name }}
     app.kubernetes.io/managed-by: {{  $.Release.Service }}
     app.kubernetes.io/version: {{  $.Chart.Version }}
-    prometheus: k8s
+    prometheus: {{ $.Release.Name }}
     role: alert-rules
   name: thanos-sidecar-rules
   namespace: {{  .Values.nfc_monitoring.prometheus.namespace }}