Update RSS template to match default

themes/v2/layouts/_default/rss.xml

@@ -37,7 +37,7 @@
     <link>{{ .Permalink }}</link>
     <description>Recent content {{ if ne .Title .Site.Title }}{{ with .Title }}in {{ . }} {{ end }}{{ end }}on {{ .Site.Title }}</description>
     <generator>Hugo</generator>
-    <language>{{ site.Language.LanguageCode }}</language>{{ with $authorEmail }}
+    <language>{{ site.Language.Locale }}</language>{{ with $authorEmail }}
     <managingEditor>{{.}}{{ with $authorName }} ({{ . }}){{ end }}</managingEditor>{{ end }}{{ with $authorEmail }}
     <webMaster>{{ . }}{{ with $authorName }} ({{ . }}){{ end }}</webMaster>{{ end }}{{ with .Site.Copyright }}
     <copyright>{{ . }}</copyright>{{ end }}{{ if not .Date.IsZero }}