fix conditional (#34)

Author: hxnyk

themes/compose/layouts/partials/opengraph.html

@@ -1,6 +1,6 @@
 {{- template "_internal/opengraph.html" . -}}
 {{- template "_internal/schema.html" . -}}
 {{- template "_internal/twitter_cards.html" . -}}
-{{- if eq (getenv "HUGO_ENV") "production" }}
-{{- template "_internal/google_analytics_async.html" . }}
-{{- end }}
+{{- if hugo.IsProduction }}
+  {{- template "_internal/google_analytics.html" . }}
+{{- end -}}