Fix deprecation warning emitted by hugo (#904)

Co-authored-by: Emruz Hossain <hossainemruz@gmail.com>

layouts/_default/single.html

@@ -157,8 +157,8 @@
       {{ end }}
 
       <!-- Keep backward compatibility with old config.yaml -->
-      {{ if site.DisqusShortname }}
-        {{ partial "comments/disqus.html" (dict (slice "disqus" "shortName")  site.DisqusShortname) }}
+      {{ if .Site.Config.Services.Disqus.Shortname }}
+        {{ partial "comments/disqus.html" (dict (slice "disqus" "shortName")  .Site.Config.Services.Disqus.Shortname) }}
       {{ end }}
 
       </div>

layouts/partials/analytics.html

@@ -56,6 +56,6 @@
 {{ end }}
 
 <!-- Keep backwards compatibility and consistency with HUGO defaults -->
-{{ if site.GoogleAnalytics }}
+{{ if .Site.Config.Services.GoogleAnalytics.ID }}
     {{ template "_internal/google_analytics.html" . }}
 {{ end }}