tpl/tplimpl: Remove deprecated method from sitemapindex.xml

Author: jmooring

tpl/tplimpl/embedded/templates/_default/sitemapindex.xml

@@ -3,8 +3,8 @@
   {{ range . }}
   <sitemap>
     <loc>{{ .SitemapAbsURL }}</loc>
-    {{ if not .LastChange.IsZero }}
-      <lastmod>{{ .LastChange.Format "2006-01-02T15:04:05-07:00" | safeHTML }}</lastmod>
+    {{ if not .Lastmod.IsZero }}
+      <lastmod>{{ .Lastmod.Format "2006-01-02T15:04:05-07:00" | safeHTML }}</lastmod>
     {{ end }}
   </sitemap>
   {{ end }}