[stable/nats] Fix ValidationError: unknown field "serviceName" (#14439)

Signed-off-by: guessi <guessi@gmail.com>

stable/nats/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v1
 name: nats
-version: 2.5.4
+version: 2.5.5
 appVersion: 1.4.1
 description: An open-source, cloud-native messaging system
 keywords:

stable/nats/templates/deployment.yaml

@@ -9,7 +9,6 @@ metadata:
     release: {{ .Release.Name | quote }}
     heritage: {{ .Release.Service | quote }}
 spec:
-  serviceName: {{ template "nats.fullname" . }}-headless
   replicas: {{ .Values.replicaCount }}
   strategy:
     rollingUpdate: