Update related.md

Closes https://github.com/gohugoio/hugo/issues/8002

content/en/content-management/related.md

@@ -84,6 +84,8 @@ related:
     weight: 10
 {{< /code-toggle >}}
 
+Note that if you have configured `tags` as a taxonomy, `tags` will also be added to the default configuration abve with the weight of `80`.
+
 Custom configuration should be set using the same syntax.
 
 {{% note %}}