Elasticsearch: do not include heritage selector (#437)

According to https://github.com/helm/charts/blob/master/REVIEW_GUIDELINES.md, service selector should not contain heritage.

It would break (future) migration from helm 2 to helm 3 (during the rolling update only, there could be a downtime when only old nodes are ready but new services is there).

elasticsearch/templates/service.yaml

@@ -20,7 +20,6 @@ metadata:
 spec:
   type: {{ .Values.service.type }}
   selector:
-    heritage: {{ .Release.Service | quote }}
     release: {{ .Release.Name | quote }}
     chart: "{{ .Chart.Name }}"
     app: "{{ template "elasticsearch.uname" . }}"