[metricbeat] only use .Chart.Version in chart label

This fix metricbeat chart upgrades when .Chart.Version change.

UPGRADE FAILED
Error: Deployment.apps "metricbeat-metricbeat-metrics" is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app":"metricbeat-metricbeat-metrics", "chart":"metricbeat-7.7.0", "heritage":"Tiller", "release":"metricbeat"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable
Error: UPGRADE FAILED: Deployment.apps "metricbeat-metricbeat-metrics" is invalid: spec.selector: Invalid value: v1.LabelSelector{MatchLabels:map[string]string{"app":"metricbeat-metricbeat-metrics", "chart":"metricbeat-7.7.0", "heritage":"Tiller", "release":"metricbeat"}, MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable

See helm/charts#7680 for more details

metricbeat/templates/deployment.yaml

@@ -13,7 +13,7 @@ spec:
   selector:
     matchLabels:
       app: '{{ template "metricbeat.fullname" . }}-metrics'
-      chart: '{{ .Chart.Name }}-{{ .Chart.Version }}'
+      chart: '{{ .Chart.Name }}'
       heritage: '{{ .Release.Service }}'
       release: '{{ .Release.Name }}'
   template:
@@ -119,4 +119,4 @@ spec:
         {{- end }}
       {{- if .Values.extraContainers }}
 {{ tpl .Values.extraContainers . | indent 6 }}
-      {{- end }}
+      {{- end }}