layouts: properly deprecate .Site.Social usage

Hugo recently started throwing an error when accessing .Site.Social.
This has been deprecated since 0.124 and will be removed in 0.137.

This package's usage to throw its own deprecation warning makes builds
with a recent hugo version fail (so pretty much everyone's)---remove it.

Signed-off-by: Luca Zeuch <l-zeuch@email.de>

.changeset/brown-keys-wait.md

@@ -0,0 +1,5 @@
+---
+"@thulite/seo": patch
+---
+
+Properly deprecate .Site.Social usage.

layouts/partials/seo/opengraph.html

@@ -41,11 +41,6 @@
   {{- if reflect.IsMap . }}
     {{- $facebookAdmin = .facebook_admin }}
   {{- end }}
-{{- else }}
-  {{- with site.Social.facebook_admin }}
-    {{- $facebookAdmin = . }}
-    {{- warnf "The social key in site configuration is deprecated. Use params.social.facebook_admin instead." }}
-  {{- end }}
 {{- end }}
 
 {{- /* Facebook Page Admin ID for Domain Insights */}}

layouts/partials/seo/twitter.html

@@ -15,11 +15,6 @@
   {{- if reflect.IsMap . }}
     {{- $twitterSite = .twitter }}
   {{- end }}
-{{- else }}
-  {{- with site.Social.twitter }}
-    {{- $twitterSite = . }}
-    {{- warnf "The social key in site configuration is deprecated. Use params.social.twitter instead." }}
-  {{- end }}
 {{- end }}
 
 {{- with $twitterSite }}